A person or persons for whatever reason have slipped to the bottom of the species intelligence grid. Possibly caused by head trauma, gestational drug use, binge drinking or simply genetic abnormalities most likely incest... Can be affected at any age and almost always permanent. The world is full of rum dumbs and nobody is policing the gene pool unfortunately!!
Oh no! Leroy fell on his head when he was younger and now he rides the short bus with the rest of the rum dumbs.
A noun referring to one who most likely has, will, or is engaging in an activity that is idiotic in nature when compared to everyone else's current activity. Much like how a group of sober people would perceive a drunk person.
"I'm going to throw that fluorescent light bulb"-Alex
"Don't throw it"- everyone else
Alex throws the light bulb and it shatters.
"Don't move police. I'm going to watch you clean that up"-Old Retired Cop
"Way to go rum-dumb"-Josh
Ruler of Lake Titicaca. Rumored to have a bunghole that gets very angry if it does not receive toilet paper. Cornholio the Great is often seen walking around with his shirt over his head and his hands in the air, chanting songs about his power, and his bunghole.
"I am Cornholio! You do not want to face the wrath of my bunghole, for I need TP!"
Butthead: Shut up, Beavis! (uh huh huh huh)
Beavis: Um, okay. (heh heh heh heh).