menstruum

noun, plural men·stru·ums, men·stru·a [men-stroo-uh, -struh] /ˈmɛn stru ə, -strə/.

1. a solvent.

noun plural -struums or -strua (-strʊə) obsolete

1. a solvent, esp one used in the preparation of a drug
2. a solid formulation of a drug

n. pl. men•stru•ums

1. A solvent, especially one used in extracting compounds from plant and animal tissues and preparing drugs.