indicatrix

英文释义

n. A certain conic section supposed to be drawn in the
tangent plane to any surface, and used to determine the accidents of
curvature of the surface at the point of contact. The curve is similar
to the intersection of the surface with a parallel to the tangent plane
and indefinitely near it. It is an ellipse when the curvature is
synclastic, and an hyperbola when the curvature is anticlastic.