sex play; erotic play
Euphemistic or literary term for sexual activity, often implying playful or lighthearted eroticism. Not a clinical term.
They were indulging in sex play.
Standard, clinical term for sexual intercourse; 桃色遊戯 is a more euphemistic, literary, and playful expression.
Casual, colloquial term for sex or lewdness; 桃色遊戯 is more formal and euphemistic, often used in literary contexts.
Compound of 桃色 (pink, a color associated with sexuality) and 遊戯 (play, game). The exact origin is uncertain, but it likely arose as a euphemistic literary coinage.