An abbreviation of "Dr. Manhattan" from the comic book and movie "Watchmen". A reference to the character always displaying his dick irl, the act of whipping out your cock forcing upon others to look.
Bro! I just got D-MATed by some brah in Kappa Omega Phi!
Dude last week, I just D-MATed it right in front of Lindsay, and she sucked me off.
{Upon being D-MATed] AH DUDE! D-MAT!!
