altitude Definition

the vertical elevation of an object above a surface (such as sea level or land) of a planet or natural satellite

the angular elevation of a celestial object above the horizon

a perpendicular line segment from a vertex of a geometric figure (such as a triangle or a pyramid) to the opposite side or the opposite side extended or from a side or face to a parallel side or face or the side or face extended

the effects (such as headache, nausea, or swelling of the brain) of oxygen deficiency in the blood and tissues developed at high altitudes having reduced atmospheric pressure

at a high altitude, where the air is thin

the height in the sky at which an airplane stays for most of a flight