"That's cap." Translation: that is a lie. Cap is slang for falsehood. It comes from African American Vernacular English, possibly from the gesture of capping a tooth or from the word "capping" meaning shooting. It spread through hip-hop and social media. "No cap" means "no lie." "Stop capping" means "stop lying." The word is short and sharp. It calls out dishonesty without a lecture.

Cap is not just for big lies. It is for exaggeration, for excuses, for empty promises. A friend says they will pay you back tomorrow. You say, "Cap." It is a joke. It is also a warning. The word is playful. It is not a serious accusation. If you are really angry, you do not say "cap." You say something else. Cap is for the small stuff.

Related slang

• No cap: for real, no lie.
• Capping: lying, exaggerating.
• Cap detector: someone who calls out lies.
• Facts: the opposite of cap, meaning truth.

Cap has a physical origin. A cap is a hat that covers your head. To "cap" can mean to cover or to top. In slang, it covers the truth. The metaphor is loose. The usage is clear. It is a word for the digital age. It is quick, funny, and skeptical. It says, "I don't believe you, but I'm not mad."