Green’s Dictionary of Slang

1. excellent, superb, best.

1948		N. Mailer Naked and Dead 21: You’re fuggin ay.
1961		(con. early 1950s) J. Peacock Valhalla 324: You fuckin’-A whoopee John!
1990		(con. early 1950s) J. Ellroy L.A. Confidential 66: Whoever coached him did a fucking-A bang-up job.

2. a general intensifier.

1970		D. Ponicsan Last Detail 171: ‘You don’t have to park your ugly fat ass on the stool next to mine.’ ‘Fucking-ay-John Ditty-Bag-well-told I don’t.’.
1986		S. King It (1987) 807: They’ll come and take you away and put you into the fucking-A loonybin.

3. right, correct.

1961		(con. early 1950s) J. Peacock Valhalla 179: ‘You fucking A,’ Poke agreed solemnly.
1974		R. Stone Dog Soldiers (1976) 238: You’re fuckin’ A. They love it.
1984		W. Diehl Hooligans (2003) 42: Yeah, fuckin’-A it’s personal.
2001		S. King Dreamcatcher 8: You’re fuckin-A.
2003		Simon & Burns ‘Hard Cases’ Wire ser. 2 ep. 4 [TV script] Hah! Fuckin’-A right!