"No cap" is a slang term that means "no lie" or "for real". It is often used to emphasize that the speaker is telling the truth and not exaggerating about something hard to believe. The term "cap" refers to a lie or falsehood, while "no cap" means "no lie" or "for real". The phrase is rooted in African American Vernacular English (AAVE), or Black speech separate from standard English. The origins of the term are uncertain, but it is believed to have originated in hip-hop culture and then spread to other aspects of African American culture before being adopted by mainstream culture.

In addition to its use to indicate that someone is telling the truth, "no cap" can also be used to describe something that has no limit. In the "Green’s Dictionary of Slang" in the 1940s, "to cap" meant "to surpass." Therefore, "cap" could be defined as the "top" or "upper limit".

Here are some examples of how to use "no cap":

• "You cant be serious right now." "I really am, no cap."
• "I know hes capping right now. Theres no way he..."

Overall, "no cap" is a slang term that is used to indicate that someone is telling the truth and not exaggerating.