A stupid person; it refers to the lack of surface area on an individual's brain. The general thought is that the more surface area (wrinkles, creases, etc.) a brain has, the smarter the person is. Conversely, a person with a smooth brain (no wrinkles) has less surface area and would therefore be stupid.

syracuse point guard Gerry McNamera

Named after the short but tenacious Syracuse point guard Gerry McNamara, a GMac is any inprobable clutch or momentous action a person pulls off, usually at the last second.

G-mac means Gangster mac. Its an ill word to throw down your homeboy. Showin dat he gangster big time.

a gaysha person who wishes he was chris brown. has a chode, has small arms, and has no game at all. only gets guys, not girls. gives blumpkins, and loves to give an alabama hot pocket.