GI slang for a joint, especially one made from a real cigarette by removing the tobacco and stuffing the wrapper with marijuana. In Saigon this usually meant Park Lanes, or menthol brands, cigarettes that weren't popular with the troops. Re-sealed in their original package, they looked like an ordinary pack of cigarettes to help troops deal with authority, but it could also be used to refer to any joint.

From the Vietnamese term 'dien cai dau,' meaning crazy, so cigarette that makes you crazy or crazy cigarette.

An embarrassed smile.