pestle (n.)

"club-shaped instrument used for pounding and breaking materials in a mortar," mid-14c. pestel, (as a surname late 13c.), from Old French pestel and directly from Latin pistillum (Medieval Latin pestellum) "pounder, pestle," related to pinsere "to pound," from PIE *pis-to-, suffixed form of root *peis- "to crush" (source also of Sanskrit pinasti "pounds, crushes," pistah "anything ground, meal," Greek ptissein "to winnow," Old Church Slavonic pišo, pichati "to push, thrust, strike," pišenica "wheat," Russian pseno "millet").

Also in old use "the leg of certain animals used for food" (14c.), hence pestle of a lark "a trifle, an unimportant matter" (1590s).

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Definitions of pestle from WordNet
pestle (n.)
machine consisting of a heavy bar that moves vertically for pounding or crushing ores;
Synonyms: stamp
pestle (n.)
a heavy tool of stone or iron (usually with a flat base and a handle) that is used to grind and mix material (as grain or drugs or pigments) against a slab of stone;
Synonyms: muller / pounder
pestle (n.)
a club-shaped hand tool for grinding and mixing substances in a mortar;
pestle (v.)
grind, mash or pulverize in a mortar;
pestle the garlic