\Di*am"e*tral\, a. [Gr. F. diam['e]tral.]
Pertaining to a diameter; diametrical.
{Diametral curve}, {Diametral surface} (Geom.), any line or
   surface which bisects a system of parallel chords drawn in
   a curve or surface.
{Diametral planes} (Crystal.), planes in which two of the
   axes lie.

\Di*am"e*tral\, n.
A diameter. [Obs.] --Sir T. Browne.