Green’s Dictionary of Slang

dead ass n.

[SE dead + -ass sfx/butt n.1 (1c)]
(US)

1. the seated rump, usu. as symbolic of laziness.

[US]L. Uris Battle Cry (1964) 127: Off your dead asses and on your dying feet.
[US](con. 1950) R. Leckie March to Glory (1962) 24: It’s about time we got off our dead asses and earned our pay.
J. Contini Beast Within 126: He’d better get off his dead ass.

2. an idler, a lazy person.

[UK](con. 1940s) G. Morrill Dark Sea Running 149: Look lively, you dead-asses.

3. one who is effectively dead; cit. 1967 implies a state of impotence.

[US]B. Hecht Sensualists (1961) 126: I was always a dead ass [...] Built for men. Every inch of me. They go crazy when they hold me, naked or dressed. And me! A lot of foam rubber without a nerve ending. Dead.
[US]N. Mailer Why Are We in Vietnam? (1970) 14: Usa women know which man has got the spring and who and which is the unfortunate dead ass.
[US]E. Torres Carlito’s Way 96: Lllod, he is a dead-ass, don’t let’s get weighted down with him.

4. a listless, de-energized person.

[US]T. Wolfe Electric Kool-Aid Acid Test (1969) 50: Trying to get some action going among these deadasses in the loony bin.

5. an utterly boring, useless person.

[US]Wentworth & Flexner DAS.
[UK](con. 1960) P. Theroux My Secret Hist. (1990) 177: So long. Dead Ass.