Legit is a slang shortening of the word legitimate (actual, genuine, legal). One could say that a person is legit (honest in his dealings) or a thing or activity is legit (real, not fake, or legally proper).t means they think you are cool. Your question was what does it mean when someone calls you it. Unlike the other people trying to tell you what the literal definition of the … word legitimate, this is the urban slang. 7 people found this useful.