Whimsical, fanciful, or capricious; acting or behaving in an unpredictable or fantastical way.
From French fantastique meaning 'fanciful' or 'whimsical,' ultimately from Greek phantastikos. This is an older English borrowing that emphasizes the playful, unpredictable quality of fantasy rather than supernatural aspects.
The word 'fantasque' almost vanished from English but survives in phrases like 'the fantasque behavior of artists'—it's the word that best captures the romantic-era idea of creative genius as beautifully weird and unpredictable.
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