kai-awase; shell-matching game
A Heian-period court game where players match pairs of clam shells by their unique patterns. Sense 2 is a historical variant emphasizing the comparison aspect.
Kai-awase is a game played by Heian-period aristocrats.
tribadism; tribbing
Colloquial and vulgar term for a sexual act between women, derived from the image of shells rubbing together.
That word is slang, and the expression 貝合わせ is sometimes used.
Standard kanji spelling.
Variant kanji spelling using 合せ instead of 合わせ.
Compound of 貝 (kai, 'shell') and 合わせ (awase, 'matching'). The vulgar sense is a metaphorical extension based on the shape and rubbing motion of shells.