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A girl who is used to being with a large group of friends, but doesn't do much except for make sure her friends don't do something "stupid". Sometimes found at parties with alcohol or at a bar. Basically the girl is her friends cockblock.They are called backstager because they are like stage managers. Making sure nothing bad happens.
Sam: I'm totally gonna bang Scott!!!

Janice: Sam you can't ! I won't let you!

Sam: Janice don't be such a backstager!
by Jezter March 02, 2010