Leftover Smile 

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

Leftover Smile by rachel2themaxx January 13, 2009

leftover smile 

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*

leftover smile by Harlequin Lovecraft February 18, 2012