Green’s Dictionary of Slang

out of sight adv.

1. utterly, thoroughly.

1836		T. Haliburton Clockmaker I 192: I told you your horse would beat me clean out of sight.
1899		Ade Fables in Sl. (1902) 4: Firmness — out of sight!
1910		O. Johnson Varmint 289: ‘Comfy?’ said Slops [...] ‘Out of sight!’.
1914		Bulletin (Sydney) 10 Sept. 48/1: Um – you’ve worked over it [i.e. a poem] a good deal! Let’s see now! Ye-es, you’ve improved it out of sight!
1985		J. Sullivan ‘Watching the Girls go by’ Only Fools and Horses [TV script] Oh well that beats me out of sight Boycie.

2. extremely well.

[1865		‘Cupid Turned Housebreaker’ in Rambler’s Flash Songster 39: What would they say, if they could see, his picklock out of sight; / The ladies’ all, both great and small, how they turn up their eyes, / They’d never dreamt, his instrument was half the size].
1896		Ade Artie (1963) 4: She treated me out o’ sight.
1900		Bulletin (Sydney) 29 Sept. 24/2: Writer will have his bit on Finland if he faces the flag, as this colt has ‘come on’ out of sight during present season, and looks like continuing to thrive.
1902		P.L. Dunbar Jest Of Fate (1903) 98: There’s a fellah in the house ’at plays rag-time out o’ sight.
1981		Bukka White q. in McKee & Chisenhall Beale Black & Blue 122: My daddy was a big performer. He played guitar, mandolin, saxophone, piano; and man, could he dance—outta sight.

In phrases