- (superl.) Hard to penetrate or comprehend; profound; -- opposed to shallow or superficial; intricate; mysterious; not obvious; obscure; as, a deep subject or plot.
- (superl.) Of penetrating or far-reaching intellect; not superficial; thoroughly skilled; sagacious; cunning.
- (superl.) Profound; thorough; complete; unmixed; intense; heavy; heartfelt; as, deep distress; deep melancholy; deep horror.
- (superl.) Extending far below the surface; of great perpendicular dimension (measured from the surface downward, and distinguished from high, which is measured upward); far to the bottom; having a certain depth; as, a deep sea.
- (superl.) Muddy; boggy; sandy; -- said of roads.
- (superl.) Low in situation; lying far below the general surface; as, a deep valley.
- (superl.) Extending far back from the front or outer part; of great horizontal dimension (measured backward from the front or nearer part, mouth, etc.); as, a deep cave or recess or wound; a gallery ten seats deep; a company of soldiers six files deep.
- (superl.) Of low tone; full-toned; not high or sharp; grave; heavy.
- (superl.) Strongly colored; dark; intense; not light or thin; as, deep blue or crimson.
- (n.) That which is profound, not easily fathomed or incomprehensible; a moral or spiritual depth or abyss.
- (n.) That which is deep, especially deep water, as the sea or ocean; an abyss; a great depth.
- (adv.) To a great depth; with depth; far down; profoundly; deeply.
Webster's Revised Unabridged Dictionary
| APA | Webster's. (2011). deep. Retrieved September 20, 2026, from http://smartdefine.org/deep/definitions/1995241 |
| Chicago | Webster's. 2011. "deep" http://smartdefine.org/deep/definitions/1995241 (accessed September 20, 2026). |
| Harvard | Webster's 2011, deep, Smart Define, viewed 20 September, 2026, <http://smartdefine.org/deep/definitions/1995241>. |
| MLA | Webster's. "deep" 27 May 2011. Web. 20 September 2026. <http://smartdefine.org/deep/definitions/1995241> |