godan verb (-ru), intransitive verb
have a secret affair; meet secretly and flirt
Rare, somewhat dated term for a clandestine romantic or flirtatious relationship. Often seen in the compound 乳繰り合う (ちちくりあう).
See also: 乳繰り合う
二人は人目を忍んで乳繰っていた。
The two were having a secret affair, hiding from others' eyes.
あの二人、こっそり乳繰り合ってるらしいよ。
I hear those two are secretly flirting with each other.