altitude
n. C / Un. the height of an object or place above sea level. You often hear this word when people talk about mountains or airplanes.
n. the vertical distance or elevation of an object or point in relation to a specified datum, typically sea level or the earth's surface.
The plane flies at a high altitude.
As the hikers reached a higher altitude, they noticed the air became thinner and much colder.
Commercial aircraft typically cruise at an altitude of thirty thousand feet to maximize fuel efficiency and avoid the turbulent weather patterns found in the lower atmosphere.
From Middle English, borrowed from Latin altitūdō (“height”), from altus (“high”).
Often used with the preposition 'at' ('at an altitude of'). When used in the plural, it typically refers to regions that are high above sea level.