deep (d?p)adj. deep·er, deep·est 1. a. Extending far downward below a surface: a deep hole in the river ice.b. Extending far inward from an outer surface: a deep cut.c. Extending far backward from front to rear: a deep walk-in refrigerator.d. Extending far from side to side from a center: a deep yard surrounding the house.e. Far distant down or in: deep in the woods.f. Coming from or penetrating to a depth: a deep sigh.g. Sports Located or taking place near the outer boundaries of the area of play: deep left field.2. Extending a specific distance in a given direction: snow four feet deep.3. Far distant in time or space: deep in the past.4. a. Difficult to penetrate or understand; recondite: a deep metaphysical theory.b. Of a mysterious or obscure nature: a deep secret; ancient and deep tribal rites.c. Very learned or intellectual; wise: a deep philosopher.d. Exhibiting great cunning or craft: deep political machinations.5. a. Of a grave or extreme nature: deep trouble; deepest deceit.b. Very absorbed or involved: deep in thought; deep in financial difficulties.c. Profound in quality or feeling: a deep trance; deep devotion.6. Rich and intense in shade. Used of a color: a deep red.7. Low in pitch; resonant: a deep voice.8. Covered or surrounded to a designated degree. Often used in combination: waist-deep in the water; ankle-deep in snow.9. Large in quantity or size; big: deep cuts in the budget.10. Sports Having a sufficient number of capable reserve players: That team is not very deep.adv.1. To a great depth; deeply: dig deep; feelings that run deep.2. Well along in time; late: worked deep into the night.3. Sports Close to the outer boundaries of the area of play: played deep for the first three innings; ran deep into their opponents’ territory.n.1. often deepsa. A deep place in land or in a body of water: drowned in the deep of the river.b. A vast, immeasurable extent: the deep of outer space.2. The extent of encompassing time or space; firmament.3. The most intense or extreme part: the deep of night.4. The ocean.5. Nautical A sounding that falls between marks on a lead line and thus corresponds to an estimated depth rather than a precise depth.Idioms: deep down At bottom; basically: Deep down, she was still a rebel. in deep water In difficulty.[Middle English dep, from Old English d?op; see dheub- in Indo-European roots.]deep?ly adv.deep?ness n.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.deep (di?p) adj1. extending or situated relatively far down from a surface: a deep pool. 2. extending or situated relatively far inwards, backwards, or sideways: a deep border of trees. 3. (Cricket) cricket relatively far from the pitch: the deep field; deep third man. 4. a. (postpositive) of a specified dimension downwards, inwards, or backwards: six feet deep. b. (in combination): a six-foot-deep trench. 5. coming from or penetrating to a great depth: a deep breath. 6. difficult to understand or penetrate; abstruse7. learned or intellectually demanding: a deep discussion. 8. of great intensity; extreme: deep happiness; deep trouble. 9. (foll by: in) absorbed or enveloped (by); engrossed or immersed (in): deep in study; deep in debt. 10. very cunning or crafty; devious: a deep plot. 11. mysterious or obscure: a deep secret. 12. (Colours) (of a colour) having an intense or dark hue13. low in pitch or tone: a deep voice. 14. go off the deep end informal a. to lose one’s temper; react angrilyb. chiefly US to act rashly15. in deep water in a tricky position or in trouble16. throw someone in at the deep end See end128n17. (Physical Geography) any deep place on land or under water, esp below 6000 metres (3000 fathoms)18. a poetic term for the ocean19. (Cricket) cricket the area of the field relatively far from the pitch20. the most profound, intense, or central part: the deep of winter. 21. a vast extent, as of space or time22. (Nautical Terms) nautical one of the intervals on a sounding lead, one fathom apartadv23. far on in time; late: they worked deep into the night. 24. profoundly or intensely25. deep down informal in reality, esp as opposed to appearance: she is a very kind person deep down. 26. deep in the past long ago[Old English d?op; related to Old High German tiof deep, Old Norse djupr] ?deeply adv ?deepness nCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014deep (dip) adj.andadv. -er, -est, n. adj. 1. extending far down from the top or surface: a deep well; a deep cut. 2. extending far in or back from the front: a deep shelf. 3. extending far in width; broad: a deep border. 4. ranging far from the earth and sun: a deep space probe. 5. having a specified dimension in depth: a tank 10 feet deep. 6. immersed or submerged (usu. fol. by in): a road deep in snow. 7. covered or immersed to a specified depth (often used in combination): standing knee-deep in mud. 8. situated far back or within: deep in the woods. 9. far back in geological history: deep time. 10. coming from far down: a deep breath. 11. made with the body bent or lowered to a considerable degree: a deep curtsy. 12. difficult to understand; abstruse: a deep allegory. 13. not superficial; profound: deep thoughts. 14. heartfelt; sincere: deep affections. 15. great in measure; intense: deep sorrow. 16. sound and heavy: deep sleep. 17. (of colors) dark and vivid: a deep red. 18. low in pitch, as sound, a voice, or the like. 19. mysterious; obscure: deep, dark secrets. 20. involved or enveloped: to be deep in debt. 21. absorbed; engrossed: deep in thought. 22. Baseball. relatively far from home plate: deep center field. 23. of or pertaining to the deep structure of a sentence. 24. larger than usual: deep discounts. adv. 25. to or at a considerable or specified depth. 26. to a depth or breadth of several such persons or things (used in combination): lined up three-deep around the block. 27. far on in time: to look deep into the future. 28. Baseball. farther than usual from home plate: The outfielders played deep. n. 29. the deep part of a body of water, esp. an area of the ocean floor having a depth greater than 18,000 ft. (5400 m). 30. a vast extent, as of space or time. 31. the part of greatest intensity, as of winter. 32. any of the unmarked levels, one fathom apart, on a deep-sea lead line. Compare mark 1 (def. 18) . 33. the deep, Literary. the sea or ocean: The deep was his final resting place. Idioms: 1. go off the deep end, a. to act without thought of the consequences. b. to become emotionally overwrought. c. to act without restraint, as by good sense or taste: The committee went off the deep end with the Christmas decorations. 2. in deep, inextricably involved. 3. in deep water, in serious trouble. [before 900; Middle English dep, Old English d?op, c. Old High German tiof, Old Norse djupr, Gothic diups] deep?ly, adv. deep?ness, n. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.