Green’s Dictionary of Slang

spaz n.

also spas, spasmo, spasmoid, spass, spazz, spazzer, spazwit
[SE spastic, one who suffers from spastic paralysis, i.e. ‘a condition in which some muscles undergo tonic spasm (sometimes resulting in abnormal posture) [...] so that voluntary movement of the part affected is difficult and poorly co-ordinated’ (OED); abbr. spastic n.]
[1960s+]

1. a spastic.

2. (student/school) one who is useless, clumsy, incompetent and is thus socially unacceptable; thus hyperspazz, spaz attack, a state of excitement.

3. (US campus) a general pej.; no physical incompetence is implied.

In derivatives

spazzy (adj.)

1. [1920s+] (also spazzed) stupid, uncontrolled, bizarre, intense, nervous (cf. spazzled adj.).

2. [1950s] good, wonderful.

3. [1990s+] lit. spastic or disabled.

In compounds

spaz cut (n.)

[1990s+] (UK juv.) an unflattering haircut.

spaz pads (n.)

[1970s+] orthopaedic shoes.

spaz-wit (n.)

[1980s+] a fool, an idiot.

In phrases

chuck a spaz (v.)

[1990s+] (Aus.) to lose one’s temper.