Green’s Dictionary of Slang

solid adv.2

completely, unreservedly.

[US]Sun (NY) 10 Oct. 2/5: Mac’s been tellin’ me that the Dagos are solid for George.
[Aus]C.J. Dennis ‘The Singing Soldiers’ in Moods of Ginger Mick 61: They’ve bin up agin it solid since we crossed the flamin’ foam.
[UK]Birmingham Dly Gaz. 22 Nov. 2/2: Vote solid for Banfield.
[UK]Motherwell Times 24 Oct. 7/1: [advert] Vote Solid for Johnstones — the Working Man’s Complete Outfitter.
[US]J. Conroy World to Win 167: They’re on strike. They’re out solid.
[US]Z.N. Hurston ‘Story in Harlem Sl.’ in Novels and Stories (1995) 1001: Skinny in the hips and solid built for speed.
[US]S. Bellow Augie March (1996) 275: You had to get tied up this way – in dutch good and solid.
[UK]C. Hooper Brief Authority 225: I’m getting drunk to-night – solid stinking plastered.
[US]D. Jenkins Semi-Tough 12: That’s really no joke that you hear. They can solid fuckin’ dance.
[UK]H.B. Gilmour Pretty in Pink 99: If I really have it solid for a girl [...] I ride by her house.