A mustache variant. Specifically, a mad dog (or Hulk Hogan if you prefer) that only combat Vietnam vets can grow after they've reached the age of 55. Only after you have looked eye ball to eye ball with the man in the black pajamas (a worthy fucking adversary) will you be able to grow this mustache.
Most, if not all, of the gentleman sporting this stache will be wearing a Vietnam Veteran hat and a pair of gold aviator sunglasses They may, or may not, also have a kick ass nickname, like "Dead Eye" or "Bunny".
The dad-stache is a unique moustache that is perhaps the pinnacle of all staches. While it appears similar to a 70s porn stache, it is not quite the same since it is not as creepy.
Males can only grow one of these badboys once they have had a kid (in particular a son). It is a biologic reaction that has evolved through the years because such a moustache commands respect from ones offspring and in general demonstrates clear bad-assery.
You kind of had this nasty scum stache vibe going on until your wife had your son. Then all the sudden you developed a wicked dad-stache that made Burt Reynolds look like a pubescent cheeseball!
A word that comes out of your mouth when your brain malfunctions because said brain is culling all processes not geared towards achieving a perfect run.
Something between spin, punch, bitch, and not even X knows what else.