Charlie is in the bush

A warning call to advise those in the surrounding areas that a Chief Petty Officer is among them collecting information to use against them at a later time.

Hush up! Charlie is in the bush.

Airman Underground

A discreet communication channel used among those in the Naval aviation pay grades E-1 thru E-3 to keep Naval aviation pay grades E-7 and above out of the loop. It often adds fuel to the fire and the cause of rumors.

I don't know who she's fucking, but I bet the airman underground knows tho.