A doogleplex is an area of the body which, when punched with sufficient accuracy and strength, will cause the victim to temporarily lose control of their body and punch, kick, and otherwise destroy everything and anything nearby until they are rendered unconscious.
This area is very commonly either the spine, the side of the head, or the nose, hence the term doogleplex (see doogle).
Bully: Hey, jackass! TAKE THIS!
* bully punches the victim in the doogleplex *
* victim attacks bully and knocks him out, then visciously attacks a nearby concrete pillar, not caring that his knuckles are squirting blood everywhere*