French knickers

(UK, Irish, Commonwealth) Women's underpants.

(UK, colloquial) Knickers.

A British adjective meaning wearing knickers (underwear) — in the same vein as 'pantied' in American English. In British English, knickers refers to women's underwear, so knickered simply means having knickers on. There's also an older obsolete sense of wearing knickerbockers (the baggy Victorian-era trousers). In modern use the term is mostly encountered in a playful or somewhat saucy context, though it's relatively mild on the scale of British sauciness. Not an offensive term, just mildly intimate.

(British) Wearing knickers; pantied.

(UK) Large girls' underpants traditionally worn as shorts during school sports activities.