知る人
Meanings
1
Refers to someone one knows personally, not necessarily a close friend. Often used in contrast with strangers or in contexts of mutual recognition.
See also: 知人 (ちじん)
He is a famous photographer known to those in the know.
Living in a town where you know no one is lonely.
2
archaic
Archaic use for a romantic partner. In modern Japanese, 恋人 or 愛人 are more common.
In old writings, there are many poems longing for one's lover.