To tremble or flinch with fear; to twitch or be jumpy due to being frightened or nervous.
雷が鳴ると犬がビクついて隠れてしまう。
When thunder roars, the dog trembles and hides.
先生が急に背後に立ったので、学生はビクついた。
Because the teacher suddenly stood behind him, the student flinched.
大きな物音に彼はビクつき、手からカップが滑り落ちた。
Startled by a loud noise, he flinched and the cup slipped from his hand.