noun which may take the genitive case particle 'no'
hottest; freshest; in vogue
Slang term used in fashion, trends, and pop culture to describe something at the peak of current popularity or freshness. Often used attributively with の.
This magazine always introduces the hottest fashion.
She likes trying the freshest makeup looks.
Compound of 最 (most) and 旬 (seasonal peak, in season). The exact origin is uncertain, but it likely emerged in fashion and trend media as a slang intensifier.