That little part of your
brain that will hear or think of something hilarious but inappropriate, which will
act as its ignition. It is then powered by your attempts to ignore it, and will accelerate, never reaching a terminal speed and only stopping when you blurt out whatever thought started it at the worst possible moment. It is related - but not linked to - that part of your
brain that inexorably broadcasts horrific images to the rest of your
brain at inconvenient times, for example: images of corpses while eating, images of your
mum during sex etc.
Called 'man motor' because there is no evidence of this phenomenon ever occurring in females.
Your
idiot thoughts during a funeral: Hey, that dude who was killed in a horrific car accident at the age of 25's wife's face kinda looks
like a pan-fried vagina.
Man motor: *click! whirr...* Yep, pan-fried vagina. Probably should tell someone that.
That one part of your
brain responsible for - and completely incapable of - inhibition: No, that's horrible.
Man Motor: *Whirrrrrrrrrrrr...* Nah, go on, it'll be
funny. You love causing egregious grief.
Inhibition: No, Man Motor, no.
Man Motor *WHHIIRRRRRRRR...* Come on, you don't know how
people will react, they might like it.
Inhibition: Please stop trying to-
Man Motor: *WWWHHHHHIIIIIRRRRRRRRRRR...* PAN-FRIED VAGINA PAN-FRIED VAGINA PAN-FRIED VAGINA
You: HEY, DEAD MAN'S WIFE, YOU LOOK
LIKE A PAN-FRIED VAGINA!
Everyone: *mortified gasps*
You, at the behest of your Man Motor: So... Anyone wanna fuck?