A mortar and pestle was a tool consisting of a bowl and a club-like object used to crush, grind, and mix solid substances.
The Akaali apothecary Riaan had a larger mortar and pestle in her apothecary shop in 2151. She kept it in a shelf under some bottles and jars. She used another one – a smaller one – to prepare her tea. (ENT: "Civilization")
In 2152, Phlox was mixing ingredients with a mortar and pestle when Travis Mayweather entered sickbay complaining of a headache. (ENT: "Singularity")
In 2268, James T. Kirk sent Pavel Chekov to obtain a mortar and pestle for Leonard McCoy. Later, the doctor used them to create a tranquilizer he was planning to use on the Earp gang. (TOS: "Spectre of the Gun")