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Referring to a girl who looks good on a "Good Day - Bad Day" basis while other females are listening in on conversation that may be friends with the girl being talked about.
Friend 1 : So what do you think about the new girl, Alyssa?

*Glances at other females around nervously.*

Friend 2 : She seems kind of a GD-BD, but today was definitely a good one.
by Legacykidd July 02, 2011
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