from the GNU version of the Collaborative International Dictionary of English
- n. the inclination or slope of the sides expressed by the height in parts of the span; as, one half pitch; whole pitch; or by the height in parts of the half span, especially among engineers; or by degrees, as a pitch of 30°, of 45°, etc.; or by the rise and run, that is, the ratio of the height to the half span; as, a pitch of six rise to ten run. Equilateral pitch is where the two sloping sides with the span form an equilateral triangle.
Sorry, no etymologies found.