Out of style or no longer popular or trendy, not conforming to current fashion standards.
From 'un-' (not) + 'fashionable' (stylish or current). 'Fashion' itself comes from Latin 'factio' meaning 'a making or doing,' evolved to mean the prevailing style.
Fashion historian's paradox: some unfashionable things eventually become vintage/retro and trendy again—the more unfashionable something becomes, the closer it is to cycling back into being fashionable.
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