The Collaborative International Dictionary of English v.0.48:

Glyoxaline \Gly*ox"a*line\, n. (Chem.)
   A white, crystalline, organic base, C3H4N2, produced by the
   action of ammonia on glyoxal, and forming the origin of a
   large class of derivatives hence, any one of the series of
   which glyoxaline is a type; -- called also oxaline.
   [1913 Webster]

WordNet (r) 3.0 (2006):

glyoxaline
    n 1: an organic base C3H4N2; a histamine inhibitor [syn:
         imidazole, iminazole, glyoxaline]