expression, noun-modifying (irregular)
cheerful (look); healthy (complexion)
Describes a bright, clear, and lively appearance, especially of a person's face or complexion. Often used in literary or descriptive contexts.
彼女の冴え冴えとした笑顔が印象的だった。
Her cheerful, radiant smile was striking.
病人とは思えないほど冴え冴えとした顔色だ。
He has such a healthy complexion that you wouldn't think he's a patient.
The base verb meaning 'to be clear, bright, or lively'. 冴え冴えとした is a reduplicated emphatic form used prenominally.
Reduplication of the verb 冴える (さえる, 'to be clear, bright') in its continuative form 冴え, followed by とした, forming an emphatic adjectival phrase.