Priest
An intermediary between Man and the Gods, a service for which they usually expect a very large tithe and, in the case of exceedingly junior priests of Offler, a share in the not so much burnt, as cooked to perfection, offering of Holy Sausage.
A tithe is technically ten per cent - most holy books say so - but most Discworld priests choose to interpret this text liberally*, as opposed to applying fundamentalist literal accuracy. In this they are not a million miles removed from some of their spiritual brethren on Roundworld.
- ie, The God could never have meant an amount THAT small should be donated to His holy works on the Disc. It's obviously a metaphor for "at least half".
As Moist von Lipwig found out to his cost.
A "priest" is also a specialised trade euphemism used by Assassins, Thieves and fishermen.
To an Assassin, "priests" are shoes with reinforced undersides which prevent the practitioner from coming to grief on a floor liberally strewn with poison-tipped caltrops - they save your soles.
To a fisherman, a "priest" is a sturdy wooden club used to give the Last Rites to a large fish desperately thrashing about in the bottom of a boat. Members of the Thieves' Guild have a similar concept.