Green’s Dictionary of Slang

big deal! excl.

[big deal n.]

(orig. US) a dismissive, sarcastic excl., ‘what’s important about that?’ ‘why bother me?’.

[US]R. Chandler Playback 195: He flicked a gold lighter at a gold-tipped cigarette. Big deal.
[US]J. Thompson Texas by the Tail (1994) 46: ‘It’s my son, dear.’ ‘Big deal.’.
[US]J. Mills Panic in Needle Park (1971) 167: What’s he giving Bobby, anyway? Needle Park. Big deal. He’s got the whole West Side. To him Needle Park is a drop in the bucket.
[US]Current Sl. I:1 5/1: Hot deal Expletive in reaction to good news.
[US]D. Goines Dopefiend (1991) 76: ‘Big deal!’ she answered sarcastically.
[US]J. Ellroy Brown’s Requiem 234: I know he’s brilliant and I know he’s an iceberg. Big fucking deal.
[US](con. 1930s–60s) H. Huncke Guilty of Everything (1998) 235: All I could think of was ‘Oh shit. Big deal. Why the fuck didn’t you people leave me alone?’.
[UK]J. Cameron It Was An Accident 194: Big fucking deal.
[UK]Guardian Weekend 29 Jan. 20: There’s no fuckin’ way. There’s nothing that anyone can say to me like ‘but he’s your dad’. Big deal.