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A showing of boredom in response to someone's excitement about something. Can also be used to describe feigning enthusiasm.
Jane: "OMG, I can't wait for the new Justin Beiber single to hit the radio, holllerrr!!!"
John:"Yeah, me too. " *YAWN*

Jane: "Umm, thanks for your nonthusiasm."
by danibfly August 25, 2010
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