Green’s Dictionary of Slang

1. in institutional contexts, one who has only a short period remaining.

1906		C. Fowler letter 18 Feb. in Tomlinson Rocky Mountain Sailor (1998) 14: Most of the Lawton's men were transferred to the Oregon, whose old crew were nearly all ‘short-timers’—men whose term of enlistment had nearly expired [...] There are a good many ‘short timers’ on the different ships in the fleet .
1948		J.L. Riordan ‘A.V.G. Lingo’ in AS XXIII:1 30: They had come to China to replace short-timers who were sweating out the Hump before Tojo’s rotation policy released numerous G.I.’s for rehabilitation in the old country.
1966		Times Recorder (Zanesville, OH) 13 Mar. 10/5: Short-timer denotes an individual whose tour of duty is growing short.
1969		J. Crumley One to Count Cadence (1987) 130: The bow of his short-timer’s ribbon, untied, drooped like a pennant in the rain.
1977		(con. 1965-66) P. Caputo Rumor of War 308: Both [dead soldiers] had had only four days left of their Vietnam tours, thus confirming the truth in the proverb, ‘You’re never a short-timer until you’re home’.
1985		(con. 1969–70) D. Bodey F.N.G. (1988) 39: I’m not the only short-timer who has them shakes.
1993		(con. 1969) N.L. Russell Suicide Charlie 5: He (Harry) was a short-timer with less than a month left in-country.
2005		B. Woodward Secret Man 25: I [...] noted that I was out of the Navy or nearly out. We called it ‘short’—meaning only a few days to go. The police were sympathetic [...] and indicated that a short-timer was entitled to one binge.

2. (US prison) one who is serving a short prison sentence; one whose sentence is nearing its end.

1907		J. London Road 99: They [long-timers] would have died after a time on the fare we ‘short-timers’ received.
1912		D. Lowrie My Life in Prison 405: There are always several hundred men who are either ‘short-timers’ or who have served large portions of their sentences.
1935		A.J. Pollock Und. Speaks n.p.: Short timer, a condemned convict on the morning of his execution.
1949		Monteleone Criminal Sl. (rev. edn).
1955		J. Ritchie ‘Try It My Way’ in Best of Manhunt (2019) [ebook] ‘Tell us what we got to lose, Warden [...] I’m the short-timer here, and I got ninety years to wait’.
1983		N. Heard House of Slammers 33: The lifers [...] had to stay here when the short-timers were gone.
1992		Bentley & Corbett Prison Sl. 12: ‘Shorttimers’ will also sometimes go to one of these units in an attempt to get away from any problems that might hinder their release and to avoid the wrath of other inmates who do not like the fact someone is going home.
1994		N. McCall Makes Me Wanna Holler (1995) 171: They got into a fight and made a short-timer miss parole.

3. one who frequents a prostitute for a brief visit, involving a single act of intercourse.

1989

(con. 1950s–60s) in G. Tremlett Little Legs 96: They [...] do the business — which is usually just ten minutes for the short-timers.

4. one who has only a short time in a given occupation or institution.

1966		Current Sl. I:3 7/1: Short timer, n. Someone whose period of servitude is growing short.
1986		C. Stroud Close Pursuit (1988) 157: He looked like a short-timer; he had a big belly and heavily veined hands.
1997		Simon & Burns Corner (1998) 69: A few of West Baltimore’s stickup men have survived a decade or more, but most carry the doomed, thousand-yard-stare of short-timers.