Green’s Dictionary of Slang

ass, the n.

also arse, the
[fig. use of ass n. (2)/abbr. red ass n. (3)]

1. (orig. US) a bad temper.

[US]R. Moore Green Berets 43: Those boys have big case of the ass with us.
B. Hersey letter 16 Mar. at 🌐 Oh well, I guess that I’ve got a case of the ‘ass’ because I am short and I want to go home. [...] The sooner that I get out of this damn troop and the 11th Cav the better I will like it.
[US](con. 1970) J.M. Del Vecchio 13th Valley (1983) 200: You fuckin airhead assholes give me a case of the ass.
P. McGowan Outside the Wire n.p.: The prisoner was a defiant sort that obviously had a case of the ass. Muhammad Qamar possessed a defiant and seething disposition.
[US] in New Yorker 12 Nov. n.p.: These guys have had a case of the ass since Mogadishu. They want to do it right and they train hard. Don’t put them on something stupid.

2. (US campus/gay) something unpleasant, a disappointment.

[US]R.O. Scott Gay Sl. Dict. 🌐 ass: [...] 6. ‘Ass, (The)’: something terrible; a let-down; ex ‘Oh my God, That was the ass!’.
[US]Eble Campus Sl. Fall 1: ASS – bad, unacceptable.

In phrases

get (the) ass (v.) (also have the ass) [abbr. get the red ass under red ass n.]

(US black/campus) to lose one’s temper, to become annoyed.

[US]Baker et al. CUSS 72: Ass, have the Angry.
[US]Current Sl. V:1 16: Get ass, v. To flare up in anger.
[US]G. Underwood ‘Razorback Sl.’ in AS L:1/2 55: ass, get the v phr Be angry.
[US]L. Heinemann Close Quarters (1987) 20: That’s why I got the ass at Surtees, ’cause that spook just took his sweet fucken time callin’ them in.
[UK]N. Griffiths Stump 74: Darren [...] Yeh still narky? Still got thee arse?