The height of an object or structure above a reference level, usually above sea level or the Earth's surface.
Astronomy The position of a celestial object above an observer's horizon, measured in degrees along a line between the horizon (0°) and the zenith (90°). Unlike declination and celestial latitude—the corresponding points in other celestial coordinate systems—the altitude of star or other celestial object is dependent on an observer's geographic location and changes steadily as the sky passes overhead due to the rotation of the Earth. See more at altazimuth coordinate system.
Mathematics The perpendicular distance from the base of a geometric figure, such as a triangle, to the opposite vertex, side, or surface.
[al-ti-tood, -tyood] 
d') Pronunciation Key
tɪˌtud