The Collaborative International Dictionary
Diametral surface
Diametral \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.