貝かい合あわせ

noun

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.

• 貝かい合あわせは平へい安あん時じ代だいの貴き族ぞくの遊あそびです。

  Kai-awase is a game played by Heian-period aristocrats.

noun

tribadism; tribbing

Colloquial and vulgar term for a sexual act between women, derived from the image of shells rubbing together.

• その単たん語ごは俗ぞく語ごで、貝かい合あわせという表ひょう現げんが使つかわれることがある。

  That word is slang, and the expression 貝合わせ is sometimes used.