The Collaborative International Dictionary of English v.0.48:

Glucinum \Glu*ci"num\, n. [Cf. F. glucinium, glycium, fr. Gr. ?,
   sweet. Cf. Glycerin.] (Chem.)
   A rare metallic element, of a silver white color, and low
   specific gravity (2.1), resembling magnesium. It never occurs
   naturally in the free state, but is always combined, usually
   with silica or alumina, or both; as in the minerals
   phenacite, chrysoberyl, beryl or emerald, euclase, and
   danalite. It was named from its oxide glucina, which was
   known long before the element was isolated. Symbol Gl. Atomic
   weight 9.1. Called also beryllium. [Formerly written also
   glucinium.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

glucinium
    n 1: a light strong brittle grey toxic bivalent metallic element
         [syn: beryllium, Be, glucinium, atomic number 4]