expression, ichidan verb
duck one's head; shrug one's shoulders
Describes pulling the head down between the shoulders, often from cold, fear, or embarrassment. The gesture can involve both head and shoulders.
See also: 竦める (すくめる)
寒くて思わず首をすくめた。
It was so cold I instinctively ducked my head.
彼は叱られて首
He apologized while shrugging his shoulders after being scolded.