A mispronounciation of "Ghillie Suit" which is a suit usually made from OD netting and burlap strips of woodland colors attached to the netting that is meant to resemble leaves, bushes and such. It is usually worn by snipers.
Kyle: I think I'm gonna get a gyle suit.
Parker: You mean a ghillie siut?
Bryon: HAHAHAHAHA! Think man. G-h-i-l-l-i-e. Ghillie suit. HAHAHA!
Kyle: STFU!!! ITS NOT THAT FUNNY!