Informal: Primarily, the word 'boob' refers to the female breast. It's often used colloquially and can be considered vulgar depending on the context and audience. Secondary meanings include a foolish or stupid person (also 'booby'). This usage is less common than the primary meaning, and can be considered offensive. The term's usage in these different contexts reflect varying degrees of formality and social acceptability.
While the primary definition holds a strong gendered association, the latter definition focuses on intellect and behaviour.
ASS SIN TIT ERR OAF
SIMP TWIT GOOF DOPE JERK
GAFFE IDIOT BOSOM TITTY BOOBY DUMMY SCHMO NINNY ERROR
NITWIT BREAST
BLUNDER KNOCKER PINHEAD
DUMBBELL BONEHEAD
SIMPLETON
NINCOMPOOP
DROPTHEBALL CHOWDERHEAD CHUCKLEHEAD