i. A form of ionospheric propagation of electromagnetic waves via its E and F layers. These layers are highly ionized and have properties of refracting electromagnetic waves back to the earth. Normally, almost all electromagnetic signals are returned to the earth at roughly equivalent angles of incidence. However, some amount of electromagnetic energy is scattered in all directions. Some energy is refracted back toward the transmitting station. Also called backscatter
ii. In a biplane, the condition in which the upper wing is mounted farther back than the lower wing. Also called a staggered wing.