Green’s Dictionary of Slang

short time n.

1. [mid-19C+] of a prostitute, the time spent with one client before taking on a new one, rather than spending a whole night with the same man; the short time allows a single copulation; thus short-time house n., a brothel.

2. [20C+] (UK prison) a short sentence, a short part of one’s sentence left to run; thus short-time pains, pre-release nerves [time n. (1)].

3. [1920s] in pl., a couple who rent a room for an hour in order to have adulterous sex.

4. [1990s+] (US prison) one who has a short sentence or whose sentence is nearing its end [time n. (1)].

In compounds

short-time girl (n.)

[1900s] a basic, cheap prostitute who satisfies her client’s immediate need and then looks for her next customer.