Green’s Dictionary of Slang

(orig. US black/prison) very much, completely, absolutely, e.g. she really loves him big time.

1928		R. Fisher Walls Of Jericho 195: He’s big-time dickty. Dickties is evil.
1959		W. Burroughs Naked Lunch (1968) 176: Let him take his purple-assed bastard and big time spend some place else.
1967		J. Breslin World of Jimmy Breslin (1968) 14: We’re going to do this big-time.
1981		Eble Campus Sl. Mar. 1: big time – very hard or intensely.
1989		G. Tate ‘The GOP Throws a Mammy-Jammy’ in Flyboy in the Buttermilk (1992) 100: When I hear of African Americans courting Reagan’s kith and kin, I don’t get happy. I worry. Big time.
1999		K. Sampson Powder 335: The guy’s fucking up big time.
1999		P. Temple Black Tide (2012) [ebook] Brendan’s going down big time.
2001		N. Griffiths Sheepshagger 239: A whole thing’s fucked up big style.
2002		J. Lerner You Got Nothing Coming 50: They try to pull this lock-down shit in Kansas and the shit would’ve jumped off big-time.
2004		P. Howard PS, I Scored the Bridesmaids 229: Got busted, Ross. Busted big-time.
2004		L. Redhead Peepshow [ebook] Jim owes me big time. This is the pits.
2008		R. Price Lush Life 272: He’d just stepped on his dick big-time .
2010		C. Hiaasen Star Island (2011) 51: Mental defective. I mean big-time.
2012		(con. 1980s) I. Welsh Skagboys 18: I’m shocked when ah tipple it’s Andy; his heid’s been stoved in, big time.
2016		V. McDermid Out of Bounds (2017) 176: ‘Some bastard leaked big time’.
2018		J.-P. Jordan Joys of War 6: The number of fights I had with other recruits. You just couldn’t back down or show any weakness. Just go, and go big-style .
2022		G.M. Graff Watergate 103: [Nixon] now held real power over the Joint Chiefs [...] [Admiral] Moorer specifically would owe him big-time.