Answer: nonplus

AnswerCrossword Clue
NONPLUSPuzzle
NONPLUSBewilder
NONPLUSPerplex
NONPLUSDumbfound
NONPLUSLeave speechless
NONPLUSFlummox
NONPLUSPuzzle.
NONPLUSConfound
NONPLUSBaffle
NONPLUSStagger
nonplusto baffle (to confound (to confuse (to perplex)))
nonplusSurprise and confuse (someone) so much that they are unsure how to react
nonplusto render utterly perplexed; puzzle completely.