(1)One of the three axes in flight, this specifies the vertical action, the up-and-down movement. (2) The angle of a propeller or rotor blade in relation to its arc; also the distance advanced by a blade in one full rotation
EESiFlo North America, Terminology and Glossary: Aviation Terms General Aviation, Pennsylvania, USA 2002. flowmeterdirectory.com/flowmeter_terminology, (Avn - Amer) {550}