Expressing anger through name calling, combining the words sack and bastard. Sack, representing testicle and tard, a short term for bastard.

A man who messes around with other men, but no one would ever know by looking or talking to him. Used by gay black men to identify masculine gay men or DL Brothas.

Basically, just a retarded ballsack face/head.
Also, used to describe a stupid person who's face/head resembles a ballsack.