down-low

or down·low

[doun-loh]Slang.
Idioms
  1. on the down low,
    1. (of a man) secretly or discreetly engaging in sex with other men.
    2. secret; discreet: Okay I'll tell you, but keep it on the down-low.

Origin of down-low

First recorded in 1990-95; down1 + low1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018