ビクッと

adverb, noun or participle which takes 'suru'

with a start; with a jump; startled

Describes a sudden, involuntary flinch or startle reaction to surprise, fear, or a sudden stimulus. Often used with verbs like する, なる, or 震える.

• 大おおきな音おとにビクッとした。

  I started at the loud noise.

• 肩かたを叩たたかれてビクッと震ふるえた。

  I flinched when someone tapped my shoulder.