whetstone

[ hwet-stohn, wet- ]
/ ˈʰwɛtˌstoʊn, ˈwɛt- /

noun

a stone for sharpening cutlery or tools by friction.
anything that sharpens: a whetstone for dull wits.

Origin of whetstone

before 900; Middle English whetston, Old English hwetstān. See whet, stone
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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British Dictionary definitions for whetstone

whetstone

/ (ˈwɛtˌstəʊn) /

noun

a stone used for sharpening edged tools, knives, etc
something that sharpens
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012