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1.
LRB
Little Rat Bastard

An abbreviation often used by correctional or mental health staff to refer to an adolescent inmate, client or patient that is unusually uncooperative, defiant, deviant, or combative.
"Inmate #2556, elopement precaution, history of fire setting and cruelty to animals and a general LRB."
by roadkill May 30, 2005