flash of stupidity Share definition Flag A brain fart, temporary lack of common sense or mature judgment. The total opposite of flash of genius. Todd: That was a real jackass moment, bro. Dewayne: Yeah, a flash of stupidity. flash of stupidity by scriptwrite1 March 18, 2011 0 0 Get merch Get the flash of stupidity mug. Buy Now — $32.95 See more merch