Green’s Dictionary of Slang

1. a wife, a mistress.

1984

Partridge DSUE (8th edn) 758/1: from ca. 1856.

2. anything one rides, esp. a dangerous and uncontrollable horse.

1856		G.J. Whyte-Melville Kate Coventry i: We ride many an impetuous steed in safety and comfort that a man would find a dangerous and uncontrollable mount [F&H].
1873		R. Broughton Nancy III 108: His horses would certainly carry me: I wonder would he give me a mount now and then.
1890		Sporting Times 5 Apr. 1/2: Wanted to have a quid on Bewicke’s mount, but the infernal bookies, hah, wouldn’t bet without I paid him first.
1898		J. Thorp ‘Little Joe, the Wrangler’ in G. Logsdon Whorehouse Bells Were Ringing (1995) 35: The boss he cut him out a mount and kindly put him on.
1906		Out West Apr. 319: I suppose you noticed my mount today [DA].
1908		‘Doss Chiderdoss’ ‘The Novelist’s Derby’ Sporting Times 30 May 1/3: My own mount was as old as myself.
1952		W.R. Burnett Little Men, Big World 151: What’s the matter, buddy-boy, couldn’t you get a mount?

3. an act of sexual intercourse.

1896

‘Confessions of a Virtuous Wife’ in Cabinet of Venus 298: Not having had a mount for three days [...] how I lay and throbbed with anticipation.

4. (US black) a promiscuous woman, who is ‘ridden’.

1980

E. Folb Runnin’ Down Some Lines 247: mount n. Sexually promiscuous female.