Angle of incidence
WordNet
noun
(1) The angle that a line makes with a line perpendicular to the surface at the point of incidence
WiktionaryText
Noun
- The angle that a straight line, ray of light, etc., meeting a surface, makes with a normal to the surface at the point of meeting.
- The angle, usually fixed, between the chord line of a wing or horizontal stabilizer and the axis of the fuselage, measured at the root. In UK called the angle of attack.