To make something unfashionable or out of style; to deprive something of its fashionable quality or appeal.
From dis- (meaning to reverse or remove) combined with fashion (style or manner). This is a back-formation creating a verb for making something no longer fashionable.
Disfashion is essentially what happens to last year's trends—what was cutting-edge on the runway becomes disfashioned the moment new styles emerge. Fashion is cyclical, but once something is disfashioned, it takes years for it to become cool again.
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