menstruum
noun
men·stru·um ˈmen(t)-strü-əm 
-strəm
plural menstruums or menstrua ˈmen(t)-strü-ə
-strə
: a substance that dissolves a solid or holds it in suspension : solvent
Word History
Etymology
Medieval Latin, literally, menses, alteration of Latin menstrua
First Known Use
1559, in the meaning defined above
Medical Definition
menstruum
noun
men·stru·um ˈmen(t)-strə(-wə)m
plural menstruums or menstrua -str(ə-w)ə
: a substance that dissolves a solid or holds it in suspension : solvent