A mockery of "hardcore" defined as a member of the National Guard (typically, though not necessarily a Guard Bum) who has served six years or more without a combat deployment, avoids deployments, or always seems to end up with cushy missions to Europe, the Baltic, or Central America. A Guard-Core Soldier or Airman is usually seen decked-out in more gear than necessary, is typically overly enthusiastic given his/her limited experiences, and frequently incorporates recruiting paraphernalia into his/her daily civilian wardrobe.
"Sergeant X is pretty Guard-Core considering he is overweight, has made a twenty year career out of the Guard and his only time spent overseas was that two-week trip to Latvia. Where does he get all those National Guard polo shirts? Why hasn't he gone to Iraq like the rest of the National Guard?"
One whose employement is generally more than the mandatory one-weekend-a-month, but less than a full-time employee of the National Guard. Guard Bums are sometimes students and can find enough money to get by working several days a month or periodically attending extra military courses for the Guard.
When asked what he does for a living, John replied "I'm just a Guard Bum until the next deployment comes along."