Green’s Dictionary of Slang

red ass n.

also r.a., red-arse

1. (N.Z.) an incompetent person.

[UK]R. Grinstead They Dug a Hole 13: The Irish sense of humour can be more than a little exasperating at times. And so it goes on. The everlasting bickering between old sweat and red arse!
[UK]D. Davin For the Rest of Our Lives 209: A man couldn’t have those bloody redarses telling him what to do.
[UK](con. WWII) J. Robinson Jack and Jamie Go to War 57: Get some service in . . . fackin’ red-arse!

2. bad temper, irritation.

[US]J. Bouton Ball Four (1981) 272: An angry man has the red ass or the R.A.
[US]G. Underwood ‘Razorback Sl.’ in AS L:1/2 64: red ass n State of irritation.
[UK]M. Amis London Fields 182: I don’t know what the chili rilienos was doing to his insides (it even means ‘red-ass’), but his tongue looked like a reefer knot.

3. a scolding.

[UK](con. 1940s) D. MacCuish Do Not Go Gentle (1962) 248: I saw Wages [...] comin’ outa the lieutenant’s tent. He got the red ass?
[US]J. Webb Fields of Fire (1980) 83: Don’t go out there thinking I was giving you a red ass. I wasn’t.

In derivatives

red-assed (adj.)

(US) very angry.

[US]D. Dempsey ‘Lang. of Traffic Policemen’ in AS XXXVII:4 271: red-assed, adj. Extremely angry.

In phrases

get the red ass (v.)

(orig. US) to bear a grievance, to be in a bad temper.

[US]L. Uris Battle Cry (1964) 92: What’s the mater, Danny, got the red ass?
[US](con. 1950) E. Frankel Band of Brothers 105: Now don’t go gettin’ the red ass.
[US]D. Jenkins Semi-Tough 9: If any of us get the red ass about something, then we ought to talk it over among ourselves without any goddam agitators or business agents.
give the red ass (v.)

to infuriate.

[US]‘Richard Hooker’ M*A*S*H (2004) 138: You all give me the red ass.
[US]C. Cook Robbers (2001) 5: He eyeballed the guy. You giving me the redass, pardner.