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1.
Receiving a smile from someone only because they were previously laughing/smiling at something else. A very embarassing mistake.
I was so happy that he smiled at me, until i realized it was just a leftover smile
by rachel2themaxx January 13, 2009
 
2.
The awkward fading smile you have when you stop laughing at someone's joke.
Mike: *tells great joke*
Julia: *laughs, then stops, being left with an awkward leftover smile slowly fading*
by Harlequin Lovecraft January 25, 2012