A-ration bagged meal issued to Marines (usually recruits or in the field) that usually contains: a sandwich (ham, turkey, and bologna are common), a hard boiled egg, fruit, and a small bag of potato chips; often served with a beverage such as juice or milk. Also used to describe a female Marine in a sleeping bag.
Andrew: Look at that bag nasty over there
Kevin: Ehh..shes not that good looking
Noun - means a "sack lunch"
Damn, I missed the roach coach, guess I'll have to eat the bag nasty
Typically, a female who makes the conscience choice to be more stuck up than she is attractive; therefore neutralizing any positive attention from the opposite sex. Also, a female participant of an M.C.J.R.O.T.C. program.
Yo Hero, there goes Bag Nasty.