also: ちちみぞ
mammary slit
Zoological term for the groove housing the mammary glands in whales, dolphins, and porpoises.
Slang term for the cleavage between breasts; often written in kana as ちちみぞ.
The mammary slit of whales serves to protect the mammary glands.
That dress has a design that emphasizes the cleavage.
Compound of 乳 (chichi, 'milk; breast') and 溝 (mizo, 'groove; furrow'). The reading にゅうこう uses the on'yomi of both characters.