nonplus

Synonyms: astonish astound baffle balk beat bewilder boggle buffalo confound daze discomfit disconcert discountenance dismay dumbfound embarrass faze floor flurry fluster frustrate get mess with one’s head muddle mystify overcome paralyze puzzle rattle rattle one’s cage stagger stick stump stun stymie take aback throw throw into tizzy thwart

Antonyms: clear up educate enlighten explain