Manganous \Man"ga*nous\, a. (Chem.)
Of, pertaining to, designating, those compounds of manganese
in which the element has a lower valence as contrasted with
{manganic} compounds; as, manganous oxide.
[1913 Webster]
{Manganous acid}, a hypothetical compound analogous to
sulphurous acid, and forming the so-called manganites.
[1913 Webster]