diametral curve 沿径曲线
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.