Green’s Dictionary of Slang

1. a temporary prison of the military police.

1777		N. Cresswell Journal (1925) 227: If I did not choose to return to Virginia with Lieutenant Noland I would be put in the provo immediately [DA].
1779		New Jersey Archives 2 Ser. III 226: Two of them made their escape, and the other two are safely lodged in the provo of the continental troops [DA].
1832		W. Dunlap A Hist. of the Amer. Theatre 43: The Jail, then called the provo, where American prisoners suffered for asserting the rights of their country, scowled on the east [DA].
1933		(con. 1860s) R. Bradford Kingdom Coming 284: Now you drag on outn de yard or I’ll git you pro-vo’ed.

2. (Aus./N.Z.) a military police officer.

1967		F.J. Hardy in Great Aus. Lover Stories 42: The Gargler is still up there fleecing Yanks right and left, especially provos.
1972		J. McNeill Old Familiar Juice (1973) 82: ‘[I]n Cairo they had this monkey [...] we named it Hunter, after our favourite provo.
1974		(con. 1940s) I. Agnew Loner 146: The provos zeroed in like hungry vultures. ‘You’re under arrest, Driscoll.’.
1996		J. Byrell Lairs, Urgers & Coat-Tuggers 214: ‘[P]rovos’ - the military police - are about as popular as the clap and just about as irritating.
2007		S. Maloney Sucked In 65: The provos beat him to a pulp in a street brawl.