nonplus(noun, verb) noun1. A state of perplexity or bewilderment. verb1. be a mystery or bewildering toSimilar word(s): amaze, baffle, beat, bewilder, dumbfound, flummox, get, gravel, mystify, perplex, pose, puzzle, stick, stupefy, vexDefinition categories: cognition, bedevil, befuddle, confound, confuse, discombobulate, fox, fuddle, throw