Definition of down-low in English:

down-low

noun

in phrase on the down-low
US
informal
  • 1On the quiet; in secret.

    ‘he kept his status as a Hell's Angel on the down-low’
    • ‘There's still the slight complication of keeping it on the down-low so that people who didn't get invited don't get their feelings hurt, but I think it will all work out.’
    • ‘But details on that are staying on the down-low until Friday.’
    • ‘Occasionally, he punctuates the flow with the more upbeat rhythms of tracks like ‘Inside’ or ‘Brotha Man,’ but mainly he keeps everything on the down-low, using an interesting mix of pop-rock and R&B.’
    • ‘A piece of news had reached the apex of its life, and I felt somewhat responsible for seeing it through from a tip on the down-low, to an op-ed piece above the fold.’
    • ‘The note-passing had to be kept on the down-low as not to alert the plentiful U.S. Border Patrol, who are ordered every February 14 to dissuade the passing of notes and gifts due to suspicions of drug trafficking.’
    1. 1.1 (of a man) concealing his homosexual tendencies.
      • ‘Black men on the down-low differ from white gays and other black homosexuals who are in the closet by not just hiding their sexual orientation, but also denying it.’
      • ‘Or perhaps they are, secretly, on the down-low.’

Origin

1990s: originally in African-American usage.