depth

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

• noun The condition or quality of being deep.
• noun The extent, measurement, or dimension downward, backward, or inward.
• noun The measurement or sense of distance from an observation point, such as linear perspective in painting.
• noun A deep part or place.
• noun The most profound or intense part or stage.
• noun Intensity; force.
• noun The severest or worst part.
• noun A low point, level, or degree.
• noun Intellectual complexity or penetration; profundity.
• noun The range of one's understanding or competence.
• noun Strength held in reserve, especially a supply of skilled or capable replacements.
• noun The degree of richness or intensity.
• noun Lowness in pitch.
• noun Complete detail; thoroughness.

from The Century Dictionary.

• noun Deepness; distance or extension, as measured
• noun A deep place, literally or figuratively; an abyss; the sea.
• noun The deepest, innermost, or most central part of anything; the part most remote from the boundary or outer limits: as, the depth of winter or of night; in the depths of a jungle or a forest.
• noun Abstruseness; obscurity; that which is not easily explored: as, the depth of a science.
• noun Immensity; infinity; intensity.
• noun Profoundness; profundity; extent of penetration, or of the capacity of penetrating: as, depth of understanding; depth of skill.
• noun In painting, darkness and richness of tone: as, great depth of color.
• noun In logic, the quantity of comprehension; the totality of those attributes which an idea involves in itself, and which cannot be taken away from it without destroying it. This use of the word was borrowed by Hamilton from certain late Greek writers.
• noun Beyond one's depth, in water too deep for safety; hence, beyond one's ability or means.

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

• noun The quality of being deep; deepness; perpendicular measurement downward from the surface, or horizontal measurement backward from the front
• noun Profoundness; extent or degree of intensity; abundance; completeness.
• noun Lowness.
• noun That which is deep; a deep, or the deepest, part or place; the deep; the middle part.
• noun (Logic) The number of simple elements which an abstract conception or notion includes; the comprehension or content.
• noun (Horology), rare A pair of toothed wheels which work together.
• noun (Aëronautics) The perpendicular distance from the chord to the farthest point of an arched surface.
• noun (Computers) the maximum number of times a type of procedure is reiteratively called before the last call is exited; -- of subroutines or procedures which are reentrant; -- used of call stacks.
• noun (Naut.) the extent of a square sail from the head rope to the foot rope; the length of the after leach of a staysail or boom sail; -- commonly called the drop of a sail.

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

• noun The vertical distance below a surface; the amount that something is deep.
• noun The distance between the front and the back, as the depth of a drawer or closet.
• noun figuratively The intensity, complexity, strength, seriousness or importance of an emotion, or situation.
• noun computing, colors The total palette of available colors.
• noun art, photography The property of appearing three-dimensional.
• noun literary, usually plural The deepest part. (Usually of a body of water.)
• noun literary, usually plural A very remote part.
• noun The most severe part.
• noun statistics The lower of the two ranks of a value in an ordered set of values.

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

• noun the intellectual ability to penetrate deeply into ideas
• noun degree of psychological or intellectual profundity
• noun (usually plural) a low moral state
• noun (usually plural) the deepest and most remote part
• noun the extent downward or backward or inward
• noun the attribute or quality of being deep, strong, or intense