Anybody in a marching band who actually enjoys participating in it. Not so much a derogatory term as a remark upon the sheer irrationality of having fun with an activity that requires so much time, sweat, and tears.
Johnny: I love measuring out yard lines on the beach so I can test my step size even when I'm away from my beloved field!
Swampfire: Whatever, marchtard.
A Marshury is an amazing friend. She will be there for you no matter what. You can always talk to her about anything you want. They will cheer you up even when you’re really sad. Marshury is a really nice friend and person to be around and will do anything with you.