Green’s Dictionary of Slang

half-assed adv.

also half-ass
[half-assed adj.]

1. (orig. US) carelessly, incompetently.

[US](con. 1920s) J.T. Farrell Young Manhood in Studs Lonigan (1936) 337: If I plan to do something, I don’t see any reason to do it half ass.
H. Steig Send Me Down 366: Even that you do half-assed.
[US]N. Mailer Why Are We in Vietnam? (1970) 133: Grizzer he eats awhile [...] and then works a little half ass at covering the carcass over.
[US]M. Herr Dispatches 54: The machine [was] running halfassed and depressed.
[US]D. Bodey F.N.G. 206: I sort of half-ass offer it to him.
[US]UGK ‘3 in the Mornin’ [lyrics] I never understood what made you think you was handlin’ / You half-ass runnin’ through my neighborhood vandlin’.
[US]L. Pettiway Workin’ It 114: I was a C student. When a test came I half-ass cheated.
[US]Source Aug. 188: Don’t misinterpret this as Beans going half-ass in the studio or not caring if he makes music.
[US]G. Hayward Corruption Officer [ebk] cap. 6: Some just leaned against the wall half-ass listening to what was being said.

2. not seriously.

[US]Larner & Tefferteller Addict in the Street (1966) 78: I was using stuff but I wasn’t hooked; it was still half-ass.

3. reasonably.

[US]E. Bunker No Beast So Fierce 91: You used to be a halfass pretty kid. You won’t be able to catch yourself a man when you get back.
[US]N. Pileggi Wiseguy (2001) 50: The places were usually half-assed connected.

In phrases