startle

befuddle, bewilder, confound, confuse, daze, discomfit, disconcert, dismay, jar, muddle, nonplus, perplex, shake up

jerk, jolt, twitch

blench, cringe, flinch, quail, recoil, shrink, spook, squinch, wince

bound, leap, spring

react, respond

appall (also appal), bowl over, dismay, floor, jolt, shake, shake up

amaze, astound, awe

chill, daunt, demoralize, dispirit, emasculate, psych (out), undo, unman, unnerve, unstring

discomfort, discompose, disconcert, disquiet, distract, distress, disturb, perturb, unsettle, upset, worry