Deumdass 

When your teacher, friend, brother or sister or parent is being stupid, and you can't say that to their face, and you say this

"You deumdass, sayin 9+10 is 21"

Deumdass by AAAAAA57 April 24, 2019

dumdass 

1 n. Corruption of "dumbass", utilized occasionally by mentally challenged AOL users. Use of this word indicates that one is a dumbass.

"OMG you are such a dumdass!"

dumdass by Ultra Sawblade November 1, 2005