Whetstone \Whet"stone`\, n. [AS. hwetst[=a]n.] A piece of stone, natural or artificial, used for whetting, or sharpening, edge tools. The dullness of the fools is the whetstone of the wits. --Shak. Diligence is to the understanding as the whetstone to the razor. --South. Note: Some whetstones are used dry, others are moistened with water, or lubricated with oil. {To give the whetstone}, to give a premium for extravagance in falsehood. [Obs.]