Epic acronym for "Good as keent" - derived from the word cunt. Used in casual conversatiom to emphise the level of one's coolness. being called a "Gak" (said as it is written) could quite possibly be the biggest, highly ranked compliment given by a mate. Used generally between guys - a way of showing their affection for another bro without sounding pussy; Gak coming from a chick is even more complimentary because any chick that knows and uses the word Gak must be a Gak herself.
Guy 1: Bro, (insert name here) seems pretty chill ae?
Guy 2: bro hes a gak
Guy 1: yeah seemed like a gak
Guy 2: yeah man, gak as.
all the other guys in the room agree that (insert name he) is DEFFINATELY a gak