sexual service of washing a partner's fingers or toes inside one's vagina
Slang term used in the context of soaplands; refers to a specific sexual service. Not used in everyday conversation.
See also: ソープランド
Apparently there is a service called 'tsuboarai' at soaplands.
Standard kanji spelling using the modern form 壺.
Variant with the older kanji form 壷; less common but still encountered.
Compound of 壺 (tsubo, 'pot' or 'vagina' in slang) and 洗い (arai, 'washing'). The exact origin is uncertain, but it likely arose within the sex industry.