expression, godan verb (-ru)
shake one's head; disagree; refuse; turn down
Physical gesture of shaking the head to indicate disagreement, refusal, or a negative answer. Often used in contexts of declining requests or expressing a negative opinion.
See also: 首を縦に振る
彼は私の提案に首を横に振った。
He shook his head at my suggestion.
頼みごとをしたら、彼女は首を横に振って断った。
When I asked her a favor, she shook her head and refused.