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A person who is in a serious relationship and continues to flirt, kiss, hang off of, or have sex with other people. Often several at the same time. This comes from the not so common phrase of someone "putting their thumbs in more then one pie."
The pie thumber would always make out with several other boys even though she had a fiance.
by Lavinia Cay February 02, 2007

Words related to pie thumber

cheater pie relationship thumb thumber unfaithful