Green’s Dictionary of Slang

pig’s arse n.1

also pig’s ass, pig’s behind
[arse n. (1)/ass n. (2)/behind n. (1)]

1. a difficult or messy situation.

[US]D. Ponicsan Last Detail 22: I wish I was going to Portsmouth instead of being stuck in this pig’s ass of a place.
[UK]S. Gee Never in My Lifetime in Best Radio Plays (1984) 71: We could have this whole pig’s arse tidied up in no time if the blokes upstairs’d see sense.
[UK]N. Griffiths Sheepshagger 157: Yewer tryin to explain things that can’t be fuckin explained [...] an makin a pig’s arse of everything.

2. (Irish) a contemptible person.

[Ire]J. Morrow Confessions of Proinsias O’Toole 78: Ma hair’ll niver grow again an’ all because that pig’s arse wanted a patsy for a shortage in last week’s collection.
[US](con. 1968) Bunch & Cole Reckoning for Kings (1989) 234: Now let’s go see that pig’s behind we call a doctor. [Ibid.] 236: He was assured a high place in almost any government that followed. Pig’s asses [...] were not necessarily guaranteed to end as bacon.