Yes, pestle is a Scrabble word!

Verb

1. Grind, mash or pulverize in a mortar

Noun

1. Machine consisting of a heavy bar that moves vertically for pounding or crushing ores

2. 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

3. A club-shaped hand tool for grinding and mixing substances in a mortar