bit

   1. a woman viewed sexually by a male

   A synonym of piece¹ but not used of a spouse. Seldom of a prostitute:

    'Opal,' said Cicero, 'Whose bit is that?' (Londres, 1928, in translation)

   Normally in a phrase such as a bit of all right (or alright for the less literate), arse, ass, crumpet, fluff, goods, hot stuff, how's your father, jam, meat, muslin, skirt, stuff, you-know-what, etc., most of which are elaborated under those headings:

    One of them... was his own bit of goods. She was a married woman whose husband was away working. (F. Richards, 1936)

   A bit on the side is a regular sexual partner other than your spouse, adverting to the side, or additional, plate served with a formal meal:

    She had been used, had been just the fun you can't get when you're married, a bit on the side. (Bradbury, 1976)

   2. (a) copulation

   By either sex:

    ... taking a little bit now and then from her husband's valet. (Condon, 1966)

   A bit of the other is not a homosexual encounter but refers to copulation with other than a regular partner:

    ... off they go to this girlie restaurant ... Duffy's not averse to a bit of the other, (le Carré, 1991)