altitude

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The height of a thing above a reference level, especially above sea level or above the earth's surface. synonym: elevation.
• noun Great height or elevation.
• noun A high location or area.
• noun Astronomy The angular distance above the observer's horizon of a celestial object.
• noun Mathematics The perpendicular distance from the base of a geometric figure to the opposite vertex, parallel side, or parallel surface.

from The Century Dictionary.

• noun Space extended upward; height; the degree or amount of elevation of an object above its foundation, the ground, or a given level; the amount or distance by which one object is higher than another: as, the altitude of a mountain or a cloud.
• noun The elevation of a point, star, or other object above the horizon, measured by the arc of a vertical intercepted between such point and the horizon.
• noun An elevation or height; anything extending far upward.
• noun Highest point or degree; full elevation.
• noun Elevation of spirit; haughty air: in this sense generally used in the plural.

from the GNU version of the Collaborative International Dictionary of English.

• noun Space extended upward; height; the perpendicular elevation of an object above its foundation, above the ground, or above a given level, or of one object above another.
• noun (Astron.) The elevation of a point, or star, or other celestial object, above the horizon, measured by the arc of a vertical circle intercepted between such point and the horizon. It is either true or apparent; true when measured from the rational or real horizon, apparent when from the sensible or apparent horizon.
• noun (Geom.) The perpendicular distance from the base of a figure to the summit, or to the side parallel to the base
• noun Height of degree; highest point or degree.
• noun Height of rank or excellence; superiority.
• noun colloq. Elevation of spirits; heroics; haughty airs.
• noun an arc of the meridian intercepted between the south point on the horizon and any point on the meridian. See Meridian, 3.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The height measured from sea level up to any given point.
• noun A vertical distance.
• noun geometry The distance measured perpendicularly from a figure's vertex to the opposite side of the vertex.
• noun astronomy The angular distance of a heavenly body above our Earth's horizon.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun angular distance above the horizon (especially of a celestial object)
• noun elevation especially above sea level or above the earth's surface
• noun the perpendicular distance from the base of a geometric figure to the opposite vertex (or side if parallel)