Definition of at altitude
: at a high altitude, where the air is thin <She trained for the race at altitude.>
Word by Word Definitions
: 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 (see vertex 2a) 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
Seen and Heard
What made you want to look up at altitude? Please tell us where you read or heard it (including the quote, if possible).