1. A liquid used as a solvent to extract or dissolve a substance, especially in alchemy or chemistry.
Usage: archaic or technical; historically used in alchemy and early chemistry
2. In historical medical or alchemical contexts, a liquid medium or vehicle for medicinal preparations.
Usage: archaic; medical/alchemical

Examples

• The alchemist used mercury as a menstruum to dissolve the metals.
• In early chemistry, alcohol served as a common menstruum for extracting plant essences.
• The apothecary prepared the tincture by selecting an appropriate menstruum for the herbs.
• Water was the menstruum of choice for many traditional remedies.
• The menstruum carried the active ingredients through the body in ancient pharmaceutical theory.