Green’s Dictionary of Slang

hard-ass n.

also hard-arse
[hard-ass v.]

1. (orig. US) a tough person, a thug.

[US]R. Crane Born of Battle 98: Ain’t he a real, genuine hard-ass [OED].
[US]C. Shafer ‘Catheads [...] and Cho-Cho Sticks’ in Abernethy Bounty of Texas (1990) 206: hardass, n. – one who is always in trouble with prison officials.
[US]E. Torres After Hours 34: Would-be hard-ass.
[US]M. Baker Nam (1982) 13: I played some football and baseball like everybody else. I was kind of a hard-ass in school.
[NZ]A. Duff One Night Out Stealing 134: Even the hard-arses in the Tavi said Sonny was a handsome little critter.
[US]C. Hiaasen Lucky You 149: Bode could be a hardass too, but he was more of a thinker.
[UK]Indep. on Sun. Culture 16 Jan. 3: Aaron Eckhart describes Neil’s father as ‘a hard-ass’.
[US]J. Lethem Fortress of Solitude 427: Dose’s bunkmate [...] was a hardass he knew from the neighborhood.
[US]W. Ellis Crooked Little Vein 105: He could be a little odd [...] but nothing like this. Bob was a hardass. [Ibid.] 183: You’re funny when you try to be a hardass.
[US]C.F. Holme ‘Night at the Royale’ in Pulp Ink [ebook] He was sick to death of all the hard-asses in his employ fighting over the Mr Black moniker.
[US]T. Robinson Hard Bounce [ebook] The guy is a hard-ass, but he’s a cop, for chrissakes’.
[Aus]T. Spicer Good Girl Stripped Bare 237: [He] is variously described as a ‘hard arse’, ‘big swinging dick’ and ‘macho bully’.
[US]C. Hiaasen Squeeze Me 31: Not wishing to be viewed as a hard-ass on the handicapped.

2. (US) an insensitive nature; a ‘thick skin’.

[US]J. Stahl Plainclothes Naked (2002) 15: If you think I’m going to answer another fucking question about anything, you’d better have a hard ass.

In phrases

give someone the hard ass (v.)

(US) to give someone a hard time.

[US]R. Blount About Three Bricks Shy of a Load 109: ‘You just piss people off.’ He said, ‘Well I don’t mean it. Bruce, you’re always giving me the hard-ass.’.