Used mostly in the Baltimore area, a blood traitor is a girl that dates from a "forbidden" school.

"Forbidden" schools include but are not limited to:

Boys Latin
Calvert
Cathedral
St. Pauls School for Boys

Most of the "offenders" either go to Bryn Mawr (BMS) or Calvert.
Alice: God, can you believe Lilly's dating a BL guy?
Kristen: I know. She's such a blood traitor. Remember the Calvert guy she dated?
by blue eyed angel September 17, 2008
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