WordNet
startle reaction
n. a complicated involuntary reaction to a sudden unexpected stimulus (especially a loud noise); involves flexion of most skeletal muscles and a variety of visceral reactions [syn: startle response]
Usage examples of "startle reaction".
Hippocampus significantly smaller, strong startle reaction, a tendency toward dissociation.
The ticcing had started up, the head jerk reminding me of the sort of startle reaction I sometimes experience when I'm on the verge of sleep.
I have read that there are two fears that cannot be trained out of us: the startle reaction upon hearing an unexpected noise, and vertigo.