Green’s Dictionary of Slang

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

1946		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!
1947		D. Davin For the Rest of Our Lives 209: A man couldn’t have those bloody redarses telling him what to do.
1988		(con. WWII) J. Robinson Jack and Jamie Go to War 57: Get some service in . . . fackin’ red-arse!

2. (US) one who is chronically irritated, a griper, a grouch.

1961

L. Schecter Roger Maris 145: Actually Maris takes deep pleasure in being known as an RA. ‘Sure I'm mad most of the time,’ he once told a magazine man.

3. bad temper, irritation.

1969		L. Schecter Jocks 23: A man from United Press International got on his nerves and Maris threatened to punch him. Maris’ red ass hit every paper in the country.
1970		J. Bouton Ball Four 272: An angry man has the red ass or the R.A.
1975		G. Underwood ‘Razorback Sl.’ in AS L:1/2 64: red ass n State of irritation.
1989		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.

4. a scolding.

1960		(con. 1940s) D. MacCuish Do Not Go Gentle (1962) 248: I saw Wages [...] comin’ outa the lieutenant’s tent. He got the red ass?
1978		J. Webb Fields of Fire (1980) 83: Don’t go out there thinking I was giving you a red ass. I wasn’t.