cap
n. uncountable B1 Intermediate Oxford US //ˈkæp// UK //kˈæp// cap
n. a slang word for a lie or an exaggeration. You use it when you think someone is not telling the truth.
n. A falsehood or exaggeration. The term is informal slang, originating in African-American Vernacular English and popularized through online culture.
He says he's a millionaire, but that's cap.
She claimed she finished the entire project in one night, but everyone in the office knew it was cap.
While his stories about his adventurous youth were entertaining, the sheer improbability of his claims led his friends to privately dismiss most of it as entertaining but obvious cap.
Usage
Commonly used in the fixed phrase 'no cap' to mean 'no lie' or 'seriously'. As a noun, it is typically used predicatively after a linking verb, as in 'That is cap'.