Green’s Dictionary of Slang

police n.

1. (Scot./US) a policeman [abbr.].

Chicago American 5 Sept. n.p.: There is a police in attendance [...] in the theatre [DA].
‘Mark Twain’ Adventures of Snodgrass 8: He was a police [DA].
[US]J. Rodgers ‘‘Blue Yodel Number 9’ 🎵 Standing on the corner, I didn’t mean no harm / Along come a police, he took me by the arm.
H.C. Branson Pricking Thumb 29: ‘I’m the police,’ he said [DA].
[US]Simon & Burns Corner (1998) 176: ‘The police on the one charge got shot,’ [...] Fran explains that the arresting officer got killed in a shooting.

2. (US prison) a prison guard.

[US] in T.I. Rubin Sweet Daddy 36: ‘He can’t go to the police.’ ‘Police?’ ‘Hacks, screws.’.
[US]Southern Illinoisan (Carbondale, IL) 7 Apr. 4/1: Prison Slang [...] Police, hack, pig, cop. Guards.
[US]S.L. Hills Tragic Magic 137: Inmates hate guards – we call them bulls, hacks, COs, shit-heads, police.
[US]Rayman & Blau Riker’s 84: I got beat up the the police [authors’ note correction officers].

SE in slang uses

In compounds

police clothes (n.)

(Irish) free second-hand clothes distributed to the poor by the police.

[Ire](con. 1930s) K.C. Kearns Dublin Tenement Life 128: But I made me Holy Communion in the police clothes that you got free cause we were so poor.
police dog (n.) [? he follows you around and offers protection]

(US) one’s fiancé.

[US]Edwardsville Intelligencer (IL) 14 Sept. 4/4: The Flappers’ Dictionary [...] Police Dog: Young man to whom one is engaged.
police pimp (n.) [pimp n. (4a)]

(Aus. Und.) an informer.

[Aus]Advocate (Melbourne) 8 Nov. 6/3: The shadowing was so close that at one time it nearly , resulted in a serious collision through the car occupied by the police pimps running into that on which the hon. member and his friends were seated.
[Aus]Truth (Sydney) 20 Nov. 4/5: Police Pimps ands Phizgigs. Once a poor devil comes under the wrath of the law but very little chance is given him of ever again earning an honest living [...] Only one thing is left them if tbey wish to keep out of gaol, and that is to tarn police pimp and informer.
[Aus]Sydney Sportsman (Surry Hills, NSW) 28 Nov. 1/1: The King-street man identified by the police pimp could neither read nor write.
[Aus]Mercury (Hobart) 10 July 6/4: I see there is a police pimp and spy taking notes of this meeting with the object of trying to put working class agitators behind the prison bars .
[Aus]Barrier Miner 31 Dec. 2/6: You police pimp, I’ll get you before many days, and I’ll fix you up, and all the police with you.
[Aus]Canberra Times 5 May 1/4: A police pimp named Lynch, who was responsible for the prosecution of Mrs. Wood at Concord, had framed many people.
[Aus]E. Curry Hysterical Hist. of Aus. 175: Actually, my dear pupils, he was a shelf, a fizgig, a top-off, or, to use more polite language, what is known as a police pimp.
[Aus]F.J. Hardy Power Without Glory 99: ’Cos we don’t have police-pimps about ’ere, that’s why. You Stacey, and you’re a bloody nark.
C. Johnson Wild Cat Falling 74: Can’t trust just anyone. Might be a police pimp laying a trap.
Ellis & Brooksbank Mad Dog Morgan 7: You know this Wendlan is a police pimp?

In phrases

police pimping (n.)

(Aus.) working as a police informer.

[Aus]Courier-Mail (Brisbane) 16 Mar. 18: It is regrettable that one who seems to have a lot of influence in police affairs should express such childish and absurd views with regard to police pimping.
[Aus]Canberra Times 14 Ap. 3/4: [headline] POLICE ‘PIMPING’ NOW UNWELCOME.