SYNONYMS
unsettle, nonplus, discomfit, catch off balance, throw off balance, take aback, unnerve, disorient, perturb, disturb, perplex, confuse, bewilder, baffle, fluster, ruffle, shake, upset, agitate, worry, dismay, put out of countenance, discountenance, discompose
surprise, take by surprise, startle, stop someone in their tracks, put someone off, put someone off their stride, put someone off their stroke, distract
embarrass, abash
informal throw, faze, make someone scratch their head, discombobulate, rattle, set someone back on their heels, psych out
archaic cause to be at a stand, gravel