(US, idiomatic, slang, euphemistic) In secret. / (US, idiomatic, slang, euphemistic) Secretly sleeping with someone other than one's partner.

A state of secrecy. / (sexuality) The state of being a man who secretly sleeps with people other than his partner.

(of a person) Undercover or lying about one's identity. / (African-American Vernacular, of a man) Purporting to be heterosexual while engaged in sex with men.

Alternative spelling of down low