Green’s Dictionary of Slang

1. (US) a blow over the head.

1897

H.E. Hamblen On Many Seas 398: Come on now, me hearties! Step lively there! Who’s next for a hair cut?

2. (US black) a week [the notional cutting of one’s hair on a weekly basis].

1944

D. Burley Orig. Hbk of Harlem Jive 12: Ole man, it’s about a tray of haircuts on the backbeat when I nixes my pad.

3. (UK prison) a short term of imprisonment, in a local prison from a few weeks to two or three months or in a convict prison for three to five years [the relatively short period and the cutting of one’s hair on arrival in prison].

1950		P. Tempest Lag’s Lex. 98: haircut. Any very short term of imprisonment. In a local prison, one or two months or weeks. in a convict prison, three to five years.
1989		J. Morton Lowspeak.

4. (US Und.) a verbal telling-off.

1962

(con. 1953–7) L. Yablonsky Violent Gang (1967) 279: He was laughed at, ridiculed, and given a ‘haircut’ (a verbal dressing down) by other old-time con men.

5. (US police/und.) theft by the police from an arrestee before his arrival at the station house.

1999

J. Maple Crime Fighter 232: To limit [. . .] the number of times a crook carrying guns, drugs, or a pocketful of cash ‘gets a haircut’ before he’s delivered to the station house, every prisoner should be given a receipt [etc].

6. (N.Z.) winding back a car’s odometer.

2003

McGill Reed Dict. of N.Z. Sl.