The Collaborative International Dictionary of English v.0.48:

minium \min"i*um\ (?; 277), n. [L. minium, an Iberian word, the
   Romans getting all their cinnabar from Spain; cf. Basque
   armine['a].] (Chem.)
   A heavy, brilliant red pigment, consisting of an oxide of
   lead, Pb3O4, obtained by exposing lead or massicot to a
   gentle and continued heat in the air. It is used as a cement,
   as a paint, and in the manufacture of flint glass. Called
   also red lead, lead tetroxide, lead orthoplumbate,
   mineral orange, mineral red, Paris red, Saturn red,
   and less definitively, lead oxide.
   [1913 Webster]

WordNet (r) 3.0 (2006):

minium
    n 1: a reddish oxide of lead (Pb3O4) used as a pigment in paints
         and in glass and ceramics [syn: red lead, minium]