vaginal secretion; pussy juice
Vulgar slang for vaginal lubrication or discharge, often used in sexual contexts. Not appropriate in polite conversation.
彼女は興奮して本気汁が溢れていた。
She was so turned on that her pussy juice was overflowing.
Compound of 本気 (ほんき, 'seriousness') and 汁 (しる, 'juice'), literally 'serious juice'. The exact origin is uncertain, but it likely arose as vulgar slang emphasizing genuine arousal.