Cap

(noun) the top of a bottle or can usually supposed to be screwed off

(verb) to say something is wrong; hitting your head with your hand up & down signaling that is "cap" which is also known as "capping"

Tim said Donald Trump is president... STFU that's so cap! He got arrested MF

Cap

(verb) To say something is wrong; to move your hand up and down on your head expressing the word "cap" which is also called "capping"
(noun) A top of a bottle or can that is usually to be screwed off the bottle or can

Tim said Donald Trump is president, and that was a huge cap. STFU Tim! He got arrested pal.