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 angular elevation of a celestial object above the horizon
: the vertical elevation of an object above a surface (as sea level or land) of a planet or natural satellite
: a perpendicular line segment from a vertex of a geometric figure (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).