Having a clear, keen mind; mentally sharp and quick to understand — a compliment for someone's intellect.
彼女は頭脳明晰で、複雑な問題も論理的に整理して説明できる。
She is mentally sharp and can organize and explain complex problems logically.
面接官は応募者の頭脳明晰さを特に評価していた。
The interviewer particularly valued the applicant's clear intelligence.
幼い頃から頭脳明晰な一面を見せていたので、周囲の期待が高かった。
He showed signs of being sharp-minded from a young age, so there were high expectations from those around him.