A phrase used to put an exclamation point on an insult. Similar in usage to "You just got burned" or "In your face"
Instead of the pleasant and friendly holiday saying "Have a Merry Christmas", when you burn someone with a horrendously powerful insult finish them off with a "Yea Merry Dissmas pal".
The phrase is most effective when used during the holiday season.
Guy 1: Boy your Mom sure is ugly
Guy 2: I'd rather have an ugly Mom then one who blows homeless people for heroin.
Guy 1: (Crying because it's true**)
Guy 2: Yea, Merry Dissmas Pal
**The truth of the burn is not necessary, it just has to be an effective insult