[deep] 
adjective -er, -est, noun, adverb, -er, -est.| 1. | extending far down from the top or surface: a deep well; a deep valley. |
| 2. | extending far in or back from the front or from an edge, surface, opening, etc., considered as the front: a deep shelf. |
| 3. | extending far in width; broad: deep lace; a deep border. |
| 4. | ranging far from the earth and sun: a deep space probe. |
| 5. | having a specified dimension in depth: a tank 8 feet deep. |
| 6. | covered or immersed to a specified depth (often used in combination): standing knee-deep in water. |
| 7. | having a specified width or number of items from front to back (often used in combination): shelves that are 10 inches deep; cars lined up at the entrance gates three-deep. |
| 8. | extending or cutting far down relative to the surface of a given object: The knife made a deep scar in the table. |
| 9. | situated far down, in, or back: deep below the surface; deep in the woods. |
| 10. | reaching or advancing far down: a deep dive. |
| 11. | coming from far down: a deep breath. |
| 12. | made with the body bent or lowered to a considerable degree: a deep bow. |
| 13. | immersed or submerged in or heavily covered with (fol. by in): a road deep in mud. |
| 14. | difficult to penetrate or understand; abstruse: a deep allegory. |
| 15. | not superficial; profound: deep thoughts. |
| 16. | grave or serious: deep disgrace. |
| 17. | heartfelt; sincere: deep affections. |
| 18. | absorbing; engrossing: deep study. |
| 19. | great in measure; intense; extreme: deep sorrow. |
| 20. | sound and heavy; profound: deep sleep. |
| 21. | (of colors) dark and vivid: a deep red. |
| 22. | low in pitch, as sound, a voice, or the like: deep, sonorous tones. |
| 23. | having penetrating intellectual powers: a deep scholar. |
| 24. | profoundly cunning or artful: a deep and crafty scheme. |
| 25. | mysterious; obscure: deep, dark secrets. |
| 26. | immersed or involved; enveloped: a man deep in debt. |
| 27. | absorbed; engrossed: deep in thought. |
| 28. | Baseball. relatively far from home plate: He hit the ball into deep center field. |
| 29. | Linguistics. belonging to an early stage in the transformational derivation of a sentence; belonging to the deep structure. |
| 30. | 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). |
| 31. | a vast extent, as of space or time. |
| 32. | the part of greatest intensity, as of winter. |
| 33. | Nautical. any of the unmarked levels, one fathom apart, on a deep-sea lead line. Compare mark 1 (def. 20). |
| 34. | the deep, Chiefly Literary. the sea or ocean: He was laid to rest in the deep. |
| 35. | to or at a considerable or specified depth: The boat rode deep in the water. |
| 36. | far on in time: He claimed he could see deep into the future. |
| 37. | profoundly; intensely. |
| 38. | Baseball. at or to a deep place or position: The outfielders played deep, knowing the batter's reputation as a slugger. |
| 39. | go off the deep end,
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| 40. | in deep,
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| 41. | in deep water,
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in deep
Seriously involved; far advanced. For example, He was in deep with the other merchants and couldn't strike out on his own, or She used her credit cards for everything, and before long she was in deep.
in deep water. Also, in over one's head. In trouble, with more difficulties than one can manage, as in The business was in deep water after the president resigned, or I'm afraid Bill got in over his head. These metaphoric expressions transfer the difficulties of being submerged to other problems. The first appears in Miles Coverdale's 1535 translation of the Book of Psalms (68:13): "I am come into deep waters." The second, which also can signify being involved with more than one can understand, dates from the 1600s. Also see over one's head.