The Collaborative International Dictionary
Angular \An"gu*lar\, a. [L. angularis, fr. angulus angle, corner. See Angle.]
Relating to an angle or to angles; having an angle or angles; forming an angle or corner; sharp-cornered; pointed; as, an angular figure.
Measured by an angle; as, angular distance.
-
Fig.: Lean; lank; raw-boned; ungraceful; sharp and stiff in character; as, remarkably angular in his habits and appearance; an angular female.
Angular aperture, Angular distance. See Aperture, Distance.
Angular motion, the motion of a body about a fixed point or fixed axis, as of a planet or pendulum. It is equal to the angle passed over at the point or axis by a line drawn to the body.
Angular point, the point at which the sides of the angle meet; the vertex.
Angular velocity, the ratio of anuglar motion to the time employed in describing.
Wikipedia
The angular aperture of a lens is the apparent angle of the lens aperture as seen from the focal point:
$$a = 2 \arctan \left( \frac {D/2} {f} \right) = 2 \arctan \left( \frac {D} {2f} \right)$$
where
f
is the focal length