whetstone, natural or manufactured stone used as an abrasive solid to sharpen tools. It is used dry, with water, or with oil. Such a stone of the finer grade used with oil is usually called an oilstone.

Whetstone, George, 1551?-1587, English dramatist and poet. His chief work, the play Promos and Cassandra (1578), is important in the development of English domestic drama and was a source for Shakespeare's Measure for Measure. Whetstone, whose works are full of grave moral utterances, was also the author of Rock of Regard (1576), a miscellany of verse and prose; A Remembrance (1577), a poem in honor of his friend George Gascoigne; An Heptameron of Civil Discourses (1582); and A Mirror for Magistrates of Cities (1584).