Closet Cheating

Basically, it's when a cheater who uses any third-party software to get an avantage on a game, but instead of blatantly cheating, they will try to completely hide the fact that they're cheating. Most typically found in the DMG+ Levels in Counter Strike: Global Offensive matchmaking.

Legit #1: yo this guy is sketchy as ♥♥♥♥
Legit #2: he's cheating.
Cheater: i'm not hacking.
Cheater's friend: he isn't hacking dude.
Cheater #2: This kid is ♥♥♥♥♥♥♥ closet cheating. And he's actually really bad at hiding it too.