(aych dee eff dee): Humour Detecting Face Deficiency. Someone who can not smile, despite how hard he/she tries. Much like plastic, it was discovered and named by accident. May be accompanied by panic attacks, major depressive disorder, or other mental/anxiety related complications.
I went to the Wanda Sykes live show with my friend and she didn't even crack a smile! I think she has HDFD.
by aychdeeeffdee July 21, 2010