Multiboobage

Any female character with more than two breasts. Term originated (or at least popularised) by The Funday Pawpet Show's Simba, whose character Arthur Bronswager sings the parody song Total Recallin' which contains the line The best part was the girl with three breasts.

If its a male character with extra equipment, you've got a Triple Nipple.

Manga

 * In the Magical Shopping Arcade Abenobashi manga, during the horror film chapter, Mune-Mune turns into a monster with several dozen breasts.

General

 * Parts of the Furry Fandom, mainly due to this being Truth In Television for most mammals.
 * It's worth noting that this is almost exclusively done with female breasts--you'll probably never see a male furry with more than two nipples, even if he's in the same drawing as a female with more than two.

Films -- Animation

 * Adult rated cartoon The Big Bang features a villain whose torso is nothing but breasts.
 * The Last Unicorn has a three-breasted harpy.
 * Gandahar has Bizarre Alien Biology with numerous breasts on a woman.
 * Played For Laughs in Adam Sandler's Eight Crazy Nights with Mrs. Triplenipple--I mean, Mrs. Selman...

Films -- Live-Action

 * Total Recall, as demonstrated by the page image.
 * The Lap Dancing kitty that Kirk beats up in Star Trek V :The Final Frontier. She might be a Draylaxian, as this unseen race is said to have three breasts.
 * A Running Gag in Paul based off the artwork of one of the characters, with various people saying Three tits. Awesome! Even the aliens. But not four. That would be weird.
 * The cheesy '80s hair sci-fi B movie Vicious Lips features a triple-breasted hooker showing off her assets near the beginning of the film.
 * Invoked in Arizona Werewolf, riffed on Mystery Science Theater 3000 as simply Werewolf. Servo mentions that the very... ample female love interest, now a werewolf, would have six breasts. Mike is both terrified and aroused by the thought.
 * The large dancer in Jabba's Palace in Return Of The Jedi was a six-breasted Askajian.
 * There actually is a porn movie named  Triceratits, but then there would have to be, now wouldn't there?
 * The ending credits of Good Luck Chuck has one of the supporting character's wife being this.
 * Inverted in Kung Pow with Whoa, who is referred to in-story as the one-boobed chick.

Literature

 * The Hitchhikers Guide To The Galaxy makes periodic references to Eccentrica Gallumbits, the Triple-Breasted Whore of Eroticon VI. Rumor has it that her erogenous zones start several miles out from her body.
 * In the Discworld novel Feet Of Clay, when Cheery notes about how hard it is to be openly female and a dwarf, Angua (a werewolf) muses internally that at least she doesn't feel like she should be wearing three bras sometimes.
 * The Uplift Universe provides us with the Tymbrimi, foxlike empaths with four breasts (derived from ancestral nipples). They can also make themselves appear more like other species (including humans) through some odd biological process.
 * The novelisation of Total Recall was not Piers Anthony's first encounter with extra boobage; a minor character in Mute is a three-breasted mutant.

Live Action TV

 * One episode of The Young Ones started off with Neil dreaming he was on a Dallas-style TV program, opening credits included. When the credits showed cast members of this imaginary program, listed actresses' roles included the Dumb Blonde With Big Tits, the Dumb Blonde With Big Tits Who Drinks Too Much, and the Big Blonde With Dumb Tits, who had breasts on the front and back of her chest (total of four).
 * Gene Roddenberry originally wanted Deanna Troi to be of the four breasted kind, but his wife convinced him that it would be a bad idea.
 * Mentioned (to an alien ambassador) in another episode by Captain Picard about how the women of a specific planet had three of them.
 * In a variant, Nursie from Black Adder II made herself a cow costume with three udders.
 * Angel. A triple-breasted whore is seen in a demon brothel in Couplet. Unfortunately she also has a Glasgow Grin. Yeesh!

Music

 * As mentioned above, the parody song Total Recallin' with the line Da best Was da girl with three breasts.
 * According to Busted's song Year 3000, triple breasted women go around naked.

Mythology

 * There are a number of ancient cultures, such as the Inca, which depicted their fertility goddesses as having multiple breasts. Scholars have debated whether the Ephesian statues of the goddess Artemis have multiple breasts as well, but the more accepted view in recent years is that the breast-like objects on the statues are part of the goddess's costume.

Newspaper Comics

 * This Dilbert strip. Is it my imagination or is everything a little bit better here?

Puppet Shows

 * The Funday Pawpet Show is the Trope Namer through an off the cuff remark turned Catch Phrase by castmember Simba. No actual multiboobage puppets have appeared on the show however. Yet....
 * As of episode 409, this is apparently true for Lilly Voop, the female fox puppet. Discovered when the resident endangered seacow and Dirty Old Man Hugh Manatee invented a new game: Honk-A-Boob.

Tabletop Games

 * A short-lived iteration of the models for the Daemonettes Warhammer Fantasy and Warhammer 40000 had anywhere from two to six breasts apiece. These were quickly changed back to more traditional styles (which could have zero, one or two breasts, most commonly one), to... mixed reactions.

Video Games

 * The Broodmothers of Dragon Age: Origins, which used to be women who were corrupted by the taint, display this trope and are completely unclothed. They are far from being arousing, however, as they are bloated, pale, vomit-smeared monstrosities with Combat Tentacles who exist only to produce thousands of darkspawn. The Mother of the Awakening expansion is only slightly less disgusting, resembling more of a conventional human female.
 * But don't try to kiss her if your mouth only opens one way.
 * Clotho, the third Sister of Fate, in God Of War. Like the above example, however, it's far from arousing. It doesn't help that her appearance here completely contradicts the original Greek myth stating that she was the most beautiful of the three Sisters.
 * A butt-ugly Alien in Duke Nukem Forever (trailer at least). Duke would still tap that.
 * Eve's pregnant form in the first Parasite Eve game dips into this territory, albeit sans nipples.
 * The Vortigaunts in Half Life, despite being extradimensional aliens, have four nipples. It's never stated whether they're females/asexual or even mammals at all though they DO have navels which would mean they're placental; then again, they ARE aliens with a third arm growing out of their chest.
 * The Nali from Unreal. While only males appear in-game, there are frescoes of Vandora, the Nali goddess of thunder.
 * The bizarre Oocca from The Legend Of Zelda Twilight Princess, which look like chickens except for their Uncanny Valley-ish human faces and their multiple sets of breasts (with exposed nipples, no less).
 * It's totally plumage, you guys, no for real, why don't you believe us, guuuuuyyyyyssssssss...
 * In The Secret Missions the Kilrathi priestess conducting the Sivar Eshrad ceremony on Firekka is shown with three sets of breasts, covered by a three-part bikini top type affair.
 * Female Iskai from Albion have two sets of breasts (and wear diagonal bras that leave two exposed), while the men have two sets of pectorals (nipples included).

Web Comics

 * Florence the wolf-girl from Freefall has at least eight mammary glands based on the number of censor bars that appear when Helix the robot's PG-rated visual system automatically protects her modesty.
 * Discussed in this Penny Arcade strip.
 * Also, Gabe finds it exciting in smaller (and utterly implausible) doses.
 * Makes an appearance in this Wurr page (second to last panel).
 * Two examples in Magellan - the first a six breasted cat-woman who helps cadets design their costumes, and utterly subverted in the second case with a six-breasted male alien, even the other characters are confused.
 * Littans in Alien Dice, have four breasts, Twins or triplets are the norm with Littans.

Web Original

 * Inevitable Rule Thirty Four example: The Multiple Breast Art Page.

Western Animation

 * In the Kramer vs. Showgirls episode of Robot Chicken, an Enterprise crewmember is enticed by the description of alien women with ten breasts apiece.
 * In the Dethklok music video Castratikron, the, er, titular monster is a Medusa-like creature with six breasts.
 * Jimmy Two- Shoes has several background characters like this.
 * This Family Guy flashback in which Meg dates the Count from Sesame Street.
 * Due to Captain Hero's tampering with the time stream in the Drawn Together episode TermsOfEndearment results in the ENTIRE HUMAN RACE becoming humanoids composed entirerly of breasts.
 * Captain Hero: Damn! I just remembered... I'm an ass man. NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO!

Real Life

 * Polymastia can cause extra nipples or even a whole extra breast.
 * Many mammals have several pairs of nipples.
 * Carrie Underwood and Mark Wahlberg each have three nipples. Mark Wahlberg considers his third nipple to be his prized possession.