one meeting; a single encounter
Refers to a single meeting or encounter, often with a nuance of a chance or significant meeting. Not commonly used in everyday conversation; more literary or formal.
That one meeting with him changed my life.
旅先での一遇が忘れられない。
I can't forget that single encounter during my travels.
once-in-a-lifetime opportunity; golden opportunity; one-in-a-million chance
Compound of 一 (one) and 遇 (meeting, encounter). The exact historical derivation is uncertain, but the kanji combination directly conveys the meaning of a single meeting.