頭あたまが冴さえる

expression, ichidan verb

be clear-headed; have a sharp mind

Describes a state where one's mind is alert, sharp, and thinking clearly. Often used in the form 頭が冴えた (clear-headed state).

• 朝あさのコーヒーを飲のむと頭あたまが冴さえる。

  Drinking morning coffee makes my mind clear.

• 彼かれは徹てつ夜や明あけなのに頭あたまが冴さえている。

  Even after staying up all night, he is clear-headed.