See under pitch surface.
(in a gear or rack) an imaginary surface forming a plane (pitch plane), a cylinder (pitch cylinder), or a cone or frustrum (pitch cone) that moves tangentially to a similar surface in a meshing gear so that both surfaces travel at the same speed.
Origin of pitch surface
First recorded in 1885–90
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019