Green’s Dictionary of Slang

handle v.

[euph.]

1. to masturbate.

[UK]Lustful Memoirs of a Young and Passionated Girl 29: She could not keep her eyes off the beauty before her however and she soon began to handle it.
[US] in G. Legman Limerick (1953) 273: There was a young girl named Miss Randall / Who thought it was beneath her to handle / A young fellow’s pole.

2. to have sexual intercourse.

[US]Current Sl. V:2.

3. (US) to manhandle.

[US]T.A. Dorgan in Zwilling TAD Lex. (1993) 108: Yer honor this man was assaulted while tryin’ to collect a bill [...] Yes yer honor they handled me.
[US]J. Lait Gangster Girl 79: You’ll bring him where we can handle him—sure an’ safe.
[US]Z.N. Hurston Dust Tracks On a Road (1995) 627: She demanded that Papa ‘handle’ some of the sisters of the church who kept cracking her about it.

4. (S.Afr.) to believe, to find credible.

[SA]P. Slabolepszy Sat. Night at the Palace (1985) 13: Can you handle it? Coach telling a player to hit the ref!

In phrases

handle up (v.)

(US teen) lit. or fig., to get on with a task.

[US]in Palm Beach Post (W. Palm Beach, FL) 13 Sept. A018/1: You ain’t got talk crazy on Facebook just go handle up cause only thing you doing is dry snitching on yourself.