Source : Webster's Revised Unabridged Dictionary (1913)

Menstruum \Men"stru*um\, n.; pl. E. {Menstruums}, L. {Menstrua}.
   [L. menstruus. See {Menstruous}.]
   Any substance which dissolves a solid body; a solvent.

         The proper menstruum to dissolve metal.  --Bacon.

         All liquors are called menstruums which are used as
         dissolvents, or to extract the virtues of ingredients
         by infusion or decoction.                --Quincy.

   Note: The use is supposed to have originated in some notion
         of the old chemists about the influence of the moon in
         the preparation of dissolvents. --Johnson.

Source : WordNet®

menstruum
     n 1: (archaic) a solvent
     2: the monthly discharge of blood from the uterus of
        nonpregnant women from puberty to menopause; "the women
        were sickly and subject to excessive menstruation"; "a
        woman does not take the gout unless her menses be
        stopped"--Hippocrates; "the semen begins to appear in
        males and to be emitted at the same time of life that the
        catamenia begin to flow in females"--Aristotle [syn: {menstruation},
         {menses}, {catamenia}, {period}, {flow}]
     [also: {menstrua} (pl)]