Simply means "proceed". The connotation is that you have full permission, or are encouraged, to do whatever it is. The phrase is used in reference to any act, and usually in response to someone asking permission to do something.
Synonyms for go ahead
On this page, you will find 30 slang terms related to go ahead. Some of the top words include: suggit, natsk, skeech, finna, Bloo, and 25 more.