| 1. | a level, as a surface of mercury, used in determining the altitudes of stars. Compare level (def. 35). |
| 2. | the bubble in a sextant or octant for aerial use. |
| 3. | Also called flight indicator, gyro horizon. Aeronautics. an instrument that indicates the banking and pitch of an aircraft with respect to the horizon. |
| artificial horizon n. An instrument displaying a line on a flight indicator that lies within the horizontal plane and about which the pitching and banking movements of an aircraft are shown. Also called gyro horizon. |