1. big up - Noun
2. big up - Verb
(informal) To become big.
(slang, transitive) To proclaim or exaggerate the importance of; to promote.
I want to big up my bro on the mic.
They're trying to big themselves up to be more than they are.
big up (plural big ups)
(slang, also big ups) Significant respect or acclaim.
I want to give a big up to my bro on the mic.