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1.
A civilian female who you can find outside of military barracks at the end of working hours or early on a Friday evening. Nobody knows how she gets on base, but everyone knows she is a slut.
Smashley is such a barracks rat. She smoked a whole pack of cigarettes waiting for someone to fuck her.
by Snake McFace February 26, 2010
 
2.
noun; used to describe some one who has no friends, and is foced to spend all they're time in the barracks.
indiv. 1 "why is Wyatt such a barraks rat?"
indiv. 2 " cuz nobody wants to be seen out with his dumb ass."
by living proof December 12, 2003
 
3.
Military slang for a soldier who in spite of being sent to a choice duty like Germany (PARTY PALACE OF THE EUROPEAN COMMAND) decides to stay in the barracks wasting valuable youth, life experience and a helluva good time out "on the economy". Usually they are young soldiers who are so far away from home for the first time.
Damn dude, here it is Octoberfest, and Hammond won't leave his room, what a barracks rat.
by ghost3x7 April 21, 2009
 
4.
girl who searches barracks looking partners with whom to engage in adult activities
That girl is a barracks rat, she's given head to everyone in my barracks.
by Annalise the Anti-Drug June 07, 2011