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The involuntary smile that forms when you know you've done something illegal
'I see that illegal smile on your face. What did you do?'
'Last night I blew up the neighbor's garbage can..and the curb'
by WolfRyder July 05, 2012
A smile that forms when you have just gotten done smoking marijana.
Yesterday, I could tell Jim had an Illegal Smile
by AlexLemoine November 06, 2010