fly under the radar 

To act sneaky and secretly without other peoples know about it. To act furtively.

Guy 1 - Have you seen those news about the mobsters of L.A.?
Guy 2 - Oh yes, I have. They were finally discovered, working undergrounds.
Guy 1 - Haha, they were flying under the radar of our city police, but sooner or later they would be found.
Guy 2 - To fly under the radar is no easy deal, here in L.A. ... One hour or other they catch you.

fly under the radar by linkc007 August 1, 2016

Fly Under the Radar 

When your about to have sex with a woman doggy style and the woman has a fat ass. To reach the pussy you must lift up her butt cheeks and fly under the radar to have sex. This can also happen when a woman have a f.u.p.a and you have to lift the f.u.p.a up to reach her pussy.

Greg: Dude your girlfriend has a fat ass! What is that like when you bang her from behind?
Jack: Well I have to Fly Under the Radar to reach her pussy.
Greg: Oh My God.

Fly Under the Radar by brendonb87 June 9, 2011