Green’s Dictionary of Slang

(orig. US prison) one who promises things, but never properly achieves them, thus one who cannot be depended upon; an ineffectual person.

1981		Maledicta V:1, 2 (Summer & Winter) 265: He also steers clear of a half-stepper, who does things half way, or a sometime, who is a person one cannot depend on.
1988		Ice-T ‘High Rollers’ 🎵 Forget the half-steppers, eject the rest.
1988		Salt-n-Pepa ‘Let The Rhythm Run’ 🎵 My partner’s name is Pep, she’s not a half-stepper.
1999		Lil O ‘Thug Niggaz’ 🎵 See I had that all my money and power, rolling over half steppers.
2010		Mocha C. Stripped 16: I was really fucking with a clown, a push-over, a punk, a half-stepper, and most of all, a pussy.
2011		Phonte ‘Everything Is Falling Down’ 🎵 King shit, Kane shit, no half-stepper.