Green’s Dictionary of Slang

a general derog., an incompetent.

1968		J. Barlow Burden of Proof 58: That was the whole point [...] Supercool. Crying was for spastics.
1970		(con. 1950s) H. Junker ‘The Fifties’ in Eisen Age of Rock 2 (1970) 102: She would certainly be turned off if he were [a] spastic.
1981		W. Boyd ‘Hardly Ever’ in On the Yankee Station (1982) 39: He considered the pool of players he could draw on: asthmatics, fatsos, spastics everyone.
1991		R. Doyle Van (1998) 585: They’ll wet themselves abou’ any ugly fucker or spastic just as long as they’re rich.
2005		B. Hare Urban Grimshaw 38: Fuck off, spastic.
2019		M. Herron Joe Country [ebook] ‘This shiftless bunch of spastics’.