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1.
The act of being sick from eating too much candy.
Nahh I can't go out tonight guys, I have a halloween hangover.
by pRad November 07, 2007
 
2.
1. The physical and mental effects of hours of excessive trick or treating or being at a halloween party.

2. The state of mind where you can't remember what went on last night at a halloween related event.
He has the halloween hangover
by TGCII October 28, 2010
 
3.
The Worst sugar crash you've ever experienced; Usually Happens the Morning after Halloween. It can be combined with alcohol.
guy 1: man, I have such a sick halloween hangover.

guy 2: Stop talking so loud!
by pwn3d_2damax November 01, 2009