noun which may take the genitive case particle 'no', noun
well-matched; becoming; suitable
Often used for couples who look good together, but also for clothes, accessories, or things that suit someone.
あの二人は本当にお似合いだね。
Those two are really well-matched, aren't they.
その帽子、あなたにとてもお似合いですよ。
That hat looks very becoming on you.
Verb meaning 'to suit' or 'to look good on'; お似合い is the polite noun/adjectival form derived from it.
Polite form of 似合い (niai), the noun form of the verb 似合う (niau, 'to suit, to match well'), with the honorific prefix お (o-).