"Stop the cap" the buzz phrase

"Stop the cap" is a slang phrase commonly used in African American Vernacular English (AAVE) and it means "stop lying" or "stop exaggerating". The word "cap" in this context is short for "caping", which means to embellish or exaggerate a story or situation. So, "stop the cap" is a way of telling someone to be honest and not exaggerate or lie about something.