Green’s Dictionary of Slang

1. (Aus./US) unbelievable, unacceptable, unpleasant, frustrating, an all-purpose negative that depends for precise meaning on context.

1966		Current Sl. I:2 6/2: Unreal, adj. Difficult, particularly a difficult college course.
1967–8		Baker et al. CUSS 183: Real, not [Ibid.] 217: Unreal Extraordinary, unusual, hard to believe.
1977		C. McFadden Serial 45: It was just unreal how he’d done it again.
1980		Eble Campus Sl. Spring 6: unreal – unpleasant, frustrating.
1993		B. Moore Lex. of Cadet Lang. 408: usage: ‘You were unreal at rugby today.’.
1999		K. Sampson Powder 383: The gigantic lifeguard smiled down on him. He was unreal.

2. (Aus./Irish//N.Z./US campus) a term of all-encompassing approbation, esp. as used by teenage girls.

1977		E. Spence A Candle for Saint Antony (1978) 44: We could have a terrific time. Vienna’s just – what’s that word you’re always using? – unreal?
1985		R.G. Barrett You Wouldn’t Be Dead for Quids (1989) 164: Catherine Hill Bay’s got unreal tubes, or lefts, or rights or something.
1987		K. Lette Girls’ Night Out (1995) 126: He must be unreal to talk to.
1998		R.G. Barrett Mud Crab Boogie (2013) [ebook] There was a general chorus of, ‘Okay Reg. Thanks Reg. Unreal’.
2004		Centralian Advocate (Darwin) 7 Sept. 2/5: It was an unreal day. We had a huge turnout from interstate.
2017		L. McInerney Blood Miracles : [L]ooking as she does, unreal in black.
2019		A. Killilea Boyo-wulf at https://boyowulf.home.blog 7 Apr. 🌐 And sure it wasn’t long at all before it was ready, the most unreal of hall buildings.