Green’s Dictionary of Slang

1. a dice cheat.

1552		G. Walker Detection of Vyle and Detestable Use of Dice Play 24: A jolly fine shift, that properly is called foysting, [...] is nothing else but a sleight to carry easily within the hand as often as the foister lies.
1608		Dekker Belman of London E3: Foysting : which is nothing else but a sleight to carry Dice easily in the hand so often as the Foister listeth.

2. (Und.) a pickpocket.

1574		J. Higgins et al. Mirror for Magistrates (1815) 483: When facing foisters fit for Tiburne fraies, Are food-sick faint, or heart-sick run their waies.
1836		A. Thornton Don Juan in London II 404: His proficiency was rewards by styling him a nypper and a foyster: the former term signifying a pick-purse or cut-purse, and the latter a pick-pocket.
1859		Matsell Vocabulum 35: foyster A pickpocket.