The Collaborative International Dictionary of English v.0.48:

Clinodiagonal \Cli`no*di*ag"o*nal\, n. [Gr. kli`nein to incline
   + E. diagonal.] (Crystallog.)
   That diagonal or lateral axis in a monoclinic crystal which
   makes an oblique angle with the vertical axis. See
   Crystallization. -- a. Pertaining to, or the direction of,
   the clinodiagonal.
   [1913 Webster]