oxygen eater

Person who is inept at everything he or she does. To be in the same room with these people is to be stupider in every sense of the word. These "oxygen eaters" are born, eat, poop, and die, while serving no purpose at all except to eat my oxygen.

TOM: Yo, is that Stevie over there? Man o' man, is that guy
a waste of space or what?
SAM: Yeah. Stevie is a real oxygen eater all right.
Completely useless...