brain fart in English dictionary brain fart Meanings and definitions of "brain fart" (idiomatic, informal) A lapse in the thought process; an inability to think or remember something clearly. (idiomatic, informal) Something ill-considered and said or done impulsively. noun (idiomatic, slang) Something ill-considered and said or done impulsively. A lapse in the thought process; an inability to think or remember something clearly more Grammar and declension of brain fart brain fart ( plural brain farts) brain fart (plural brain farts) more Sample sentences with "brain fart" Declension Stem Match words all exact any Try again Available translations Finnish French German Greek Hungarian Russian Spanish Swedish Authors