I've Heard of That! What Is It?

"Private: We're going for yummy snow cones, Marlene. Wanna come? Marlene: Snow cones? Oh, snow cones are the best! Real quick: A snow cone is…?"

- The Penguins of Madagascar, "Otter Gone Wild"

A character (often The Ditz) encounters a word or phrase, and makes some comment expressing what he thinks about the thing the word refers to — just before revealing that actually, he doesn't know the word at all. ("Lorem Ipsum is terrible! By the way, what's Lorem Ipsum?")

If the character doesn't outright imply that he knows what the thing is, but is willing to venture a guess, that guess will likely be Is It Something You Eat? While that trope overlaps with this one, it generally involves an honest uncertainty, while this one is about dishonest certainty ("Of course I know that gazebos are something you eat.")

The thing in question just might turn out to be a Henway.

Sub-Trope of Feigning Intelligence, although the feigning is usually quite brief before the character admits she really doesn't know what she's talking about. Not to be confused with Malaproper, which is when the character misuses words without knowing that he don't know what the words mean (honest, but false, certainty). Completing the quadrangle is Obfuscating Stupidity, which is dishonest uncertainty/ignorance.

Anime
"Naru: Did you hear? Sailor V stopped another robbery! Usagi: That's so cool! Naru: Isn't it? Usagi: What's a Sailor V?"
 * Yotsuba&!: Upon being told that they got tickets to Water World, Yotsuba says, "Ohhh! That place!?" Jumbo asks whether she knows it: "… Not really."
 * In one episode of Di Gi Charat Nyo, the town is out of natto, so Gramps suggests going to the next town over to get some. Gran immediately gets spooked, but then asks, "Where is the next town, anyway?"
 * In Black Butler, while investigating Jack the Ripper, Ciel announces to his companions that to get information on the killer they must go see…and Lau reacts in shock/horror. When they reach the location of their informant (the Undertaker), Lau finally asks, "So where are we?"
 * Lau does this all the time.
 * The first episode of Sailor Moon had this exchange.

Film
"Giselle: I want to go on a date. Edward: (excited voice) A date! … What's a date?"
 * In Enchanted:

Live Action TV
"Dean: The prize was a Blu-ray DVD player... but it got stolen. So now it's TBD! Troy: I want TBD! Is that new?"
 * On How I Met Your Mother, Ted once gushed about how his current Girl of the Week was taking classes in Krav Maga [an Israeli system of hand-to-hand combat]. When she leaves, he admits that he doesn't really know what it is, but presumes it's some kind of yoga. He later finds out when.
 * On Community we get this exchange:

"Guard: Soon, you will be interrogated by Captain Tancredi. The Doctor: Captain Tancredi?! Guard: Do you know him? The Doctor: No."
 * One of Max's Catch Phrases on Get Smart was "A [X]! Of course, a [X]! Just one thing-- what's a [X]?"
 * In the Doctor Who serial City of Death:


 * On Lost, Sawyer reacts badly to the news he has hyperopia... but asks what it is.

Newspaper Comics

 * In a Calvin and Hobbes strip, Calvin is told that dinner will be tortellini, and complains at length about how disgusting it is. In the last panel, he's looking up the word in the dictionary.

Radio
"Major Bloodnok: Neddie Seagoon? I didn't recognise you! Ned Seagoon: Why not? Bloodnok: I've never seen you before!"
 * Pulled several different ways on the Goon Show, including:

Theater

 * In the musical The Book of Mormon, upon hearing that he and his mission companion are being sent to Uganda, Elder Cunningham exclaims "Uganda? COOL! ...where is that."

Toys
"Pohatu: A Toa? Oh great, I've always wanted to be a Toa! Just one thing... What's a Toa?"
 * Pohatu does this as a Running Gag in Bionicle:

"Pohatu: ...What's a Bohrok?"
 * Later...

"Pohatu: ...What's a Rahkshi?"
 * And again:

"Pohatu: ...What's a Solek?"
 * One more time:

Web Comics
"Tedd (jumping): Catnip!!!! Grace (joining him): Yay catnip!!! ...what's catnip?"
 * El Goonish Shive has a case of this in the mini-arc "Catnip":

Web Original

 * The Tale of the Dread Gazebo is based around this Trope.

Western Animation
"Leela: That's Zapp Brannigan's ship. Fry: The Zapp Brannigan? Leela: Uh-huh. Fry: Who's the Zapp Brannigan?"
 * Futurama, "Love's Labours Lost In Space":

"Patrick: Opposite Day? Hey, I've heard of that! SpongeBob: Really? Patrick: No! What is it?"
 * SpongeBob SquarePants, "Opposite Day":

"Ferb: What's the deal with airline food? [Audience laughs.] Stacy: (laughing) What's airline food?"
 * In "Tea at the Treedome", Sandy mentions that she needs to breathe air, and SpongeBob replies, "Me too!" Then he goes to Patrick and asks him what air is. Naturally, Patrick gives him the wrong information and Hilarity Asphyxiation Ensues.
 * The quote at the top of this page, from The Penguins of Madagascar. Marlene, having been born in captivity, is shown to be completely unfamiliar with life outside the zoo..
 * In the My Little Pony Friendship Is Magic episode "The Ticket Master," Rarity tells Pinkie Pie and Twilight Sparkle that The Grand Galloping Gala is where she's destined to meet "Him!" Pinkie Pie immediately echoes her with an admiring "Him!" only to follow it with "Who?"
 * Pinkie Pie has a similar reaction in "Sonic Rainboom" on hearing about the titular stunt Rainbow Dash is trying to master.
 * In one episode of the 2010 Pound Puppies, McLeish describes his plans for an adoption fair, and Olaf approves: "I just love adoption fairs. Even though I've never been to one before. In fact, I don't even know what one is."
 * Phineas and Ferb, "Cheer Up, Candace!": Candace and Stacy are in a comedy club Phineas and Ferb built in their efforts to cheer up Candace:


 * GIR from Invader Zim pulls this quite a lot. Often with things that he has previously proven beyond all doubt that he understands.
 * In the Aladdin sequel The Return of Jafar, after Sultan announces that he wants to make Aladdin the royal vizier, Genie pretends to be a newsman and souvenir seller announcing the new Royal Vizier and repeating the phrase several times, only to turn to Sultan afterwards and ask "What's a royal vizier?"
 * In Archer, when Sterling reveals he has cancer, everyone gasps. Then Cheryl/Carol asks what cancer is. Later in the episode, she still doesn't know what cancer is.
 * In the King of the Hill episode "Texas City Twister" when Hank and Bobby drive to the Megalo Mart to buy some fuel filters a riot has broken out because of the tornado and Hank reluctantly purchases a pack for 60 dollars, when suddenly an old woman runs up to the counter and says "Hurry honey this jackass is buying all the fuel filters!", her husband replies "Leave some for us jackass!" and a woman says "I need a fuel filter!, what are they for?, I need one!".