Green’s Dictionary of Slang

furrow n.

the vagina.

[UK]Pasquil’s Nightcap (1877) 33: Within her furrowes haue there plow’d so manie, That for to reape the crop she knowes not anie?
[UK]Cleland Memoirs of a Woman of Pleasure (1985) 165: Mad, and wild, like an over-driven steer, he ploughs up the tender furrow.
[UK] ‘The Ploughman’ in Burns Merry Muses of Caledonia (1965) 146: I’ll cleave it up, and hit it down, And water-furrow’ fair, jo ... I hae three ousen in my plough, Three better ne’er plough’d ground, jo. The foremost ox is lang and sma’, The twa are plump and round, jo’.
[UK]C. Deveureux Venus in India I 97: As my fingers pressed in Cupid’s furrow, the lovely little clitoris, ever on the watch, had sprung up to salute it with a moist and eager kiss.
[UK]Farmer Vocabula Amatoria (1966) 108: Entonnoir. The female pudendum; ‘the furrow’.
[US]Maledicta IV:2 (Winter) 182: The simplest words in common use for this ‘nasty thing’ [...] are those accepting the female sexual apparatus as a simple receptacle. These include [...] furrow, ditch, gutter.

In phrases

die in the furrow (v.) (also fail in the furrow)

of a man, to lose one’s erection during intercourse.

[UK]Farmer & Henley Sl. and Its Analogues.
[UK]Partridge DSUE (1984) 437/2: C.19–20 ob.