[flat-out] 
| 1. | moving or working at top speed or with maximum effort; all-out: a flat-out effort by all contestants. |
| 2. | downright; thoroughgoing: Many of the paintings were flat-out forgeries. |
[flat] adjective, flat⋅ter, flat⋅test, noun, verb, flat⋅ted, flat⋅ting, adverb | 1. | horizontally level: a flat roof. |
| 2. | level, even, or without unevenness of surface, as land or tabletops. |
| 3. | having a surface that is without marked projections or depressions: a broad, flat face. |
| 4. | lying horizontally and at full length, as a person; prostrate: He was flat on the canvas after the knockdown. |
| 5. | lying wholly on or against something: The banner was flat against the wall. |
| 6. | thrown down, laid low, or level with the ground, as fallen trees or buildings. |
| 7. | having a generally level shape or appearance; not deep or thick: a flat plate. |
| 8. | (of the heel of a shoe) low and broad. |
| 9. | spread out, as an unrolled map or the open hand. |
| 10. | deflated; collapsed: a flat tire. |
| 11. | absolute, downright, or positive; without qualification: a flat denial. |
| 12. | without modification or variation: a flat rate. |
| 13. | Informal. lacking money; broke. |
| 14. | without vitality or animation; lifeless; dull: flat writing. |
| 15. | having lost its flavor, sharpness, or life, as wine or food; stale. |
| 16. | (of a beverage) having lost its effervescence. |
| 17. | without flavor; not spiced: flat cooking. |
| 18. | prosaic, banal, or insipid: a flat style. |
| 19. | pointless, as a remark or joke. |
| 20. | commercially inactive: a flat day in the stock market. |
| 21. | (of a painting) not having the illusion of volume or depth. |
| 22. | (of a photograph or painting) lacking contrast or gradations of tone or color. |
| 23. | (of paint) without gloss; not shiny; mat. |
| 24. | not clear, sharp, or ringing, as sound or a voice. |
| 25. | lacking resonance and variation in pitch; monotonous: a flat delivery of the speech. |
| 26. | Music.
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| 27. | Grammar. derived without change in form, as English to brush from the noun brush and adverbs that do not add -ly to the adjective form as fast, cheap, and slow. |
| 28. | Phonetics. lenis; voiced. |
| 29. | Nautical. (of a sail)
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| 30. | flat a, the a-sound (a) of glad, bat, or act. |
| 31. | something flat. |
| 32. | a shoe, esp. a woman's shoe, with a flat heel or no heel. |
| 33. | a flat surface, side, or part of anything: He struck me with the flat of his hand. |
| 34. | flat or level ground; a flat area: salt flats. |
| 35. | a marsh, shoal, or shallow. |
| 36. | Music.
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| 37. | Theater. a piece of scenery consisting of a wooden frame, usually rectangular, covered with lightweight board or fabric. |
| 38. | a broad, thin book, chiefly for children: a juvenile flat. |
| 39. | Informal. a deflated automobile tire. |
| 40. | (in postal use) a large flat package, as in a manila envelope, for mailing. |
| 41. | Architecture. a flat roof or deck. |
| 42. | Nautical.
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| 43. | Shipbuilding.
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| 44. | an iron or steel bar of rectangular cross section. |
| 45. | Textiles. one of a series of laths covered with card clothing, used in conjunction with the cylinder in carding. |
| 46. | Photography. one or more negatives or positives in position to be reproduced. |
| 47. | Printing. a device for holding a negative or positive flat for reproduction by photoengraving. |
| 48. | Horticulture. a shallow, lidless box or tray used for rooting seeds and cuttings and for growing young plants. |
| 49. | a similar box used for shipping and selling fruits and vegetables. |
| 50. | Football. the area of the field immediately inside of or outside of an offensive end, close behind or at the line of scrimmage. |
| 51. | flats, Informal. flat races between horses. Compare flat race. |
| 52. | to make flat. |
| 53. | Music. to lower (a pitch), esp. one half step. |
| 54. | to become flat. |
| 55. | in a flat position; horizontally; levelly. |
| 56. | in a flat manner; positively; absolutely. |
| 57. | completely; utterly: flat broke. |
| 58. | exactly; precisely: She ran around the track in two minutes flat. |
| 59. | Music. below the true pitch: to sing flat. |
| 60. | Finance. without interest. |
| 61. | flat in, Nautical. to pull the clew of (a fore-and-aft sail) as nearly amidships as possible. Also, flatten in. |
| 62. | fall flat, to fail to produce the desired effect; fail completely: His attempts at humor fell flat. |
| 63. | flat aft, Nautical. trimmed so that fore-and-aft sails present as flat a surface as possible, as in sailing close to the wind. |
| 64. | flat on one's back. back (def. 19). |
| 65. | flat out, Informal.
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| flat out adv. Informal
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flat
Of, relating to, or being a market maker's inventory position that is neither long nor short; that is, the inventory is zero.
Of, relating to, or being a bond that trades without accrued interest. For example, bonds of a company in bankruptcy proceedings trade flat. A bond trading flat is indicated in bond transaction tables by the symbol f.
flat out
In a direct manner, bluntly. For example, He told the true story flat out. [Colloquial; mid-1900s]
At top speed, as in She was running flat out to catch the train. [Slang; c. 1930]