Synonym: baggy, droopy, dull, hanging, inactive, lax, lazy, loose, slow. Antonym: tight. Similar words: slacken, lack, black, flack, lackey, blacken, lacking, black out. Meaning: [slæk] 
n. 1. dust consisting of a mixture of small coal fragments and coal dust and dirt that sifts out when coal is passed over a sieve 2. a noticeable deterioration in performance or quality 3. a stretch of water without current or movement 4. a soft wet area of low-lying land that sinks underfoot 5. the condition of being loose (not taut) 6. a cord or rope or cable that is hanging loosely. v. 1. avoid responsibilities and work, be idle 2. be inattentive to, or neglect 3. release tension on 4. make less active or fast 5. become slow or slower 6. make less active or intense 7. become less in amount or intensity 8. cause to heat and crumble by treatment with water. adj. 1. not tense or taut 2. lacking in strength or firmness or resilience 3. flowing with little speed as e.g. at the turning of the tide 4. lacking in rigor or strictness.
n. 1. dust consisting of a mixture of small coal fragments and coal dust and dirt that sifts out when coal is passed over a sieve 2. a noticeable deterioration in performance or quality 3. a stretch of water without current or movement 4. a soft wet area of low-lying land that sinks underfoot 5. the condition of being loose (not taut) 6. a cord or rope or cable that is hanging loosely. v. 1. avoid responsibilities and work, be idle 2. be inattentive to, or neglect 3. release tension on 4. make less active or fast 5. become slow or slower 6. make less active or intense 7. become less in amount or intensity 8. cause to heat and crumble by treatment with water. adj. 1. not tense or taut 2. lacking in strength or firmness or resilience 3. flowing with little speed as e.g. at the turning of the tide 4. lacking in rigor or strictness. 
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31. As business was slack she packed up early.
32. He's been getting slack and making silly mistakes.
33. Winter is the slack season at most hotels.
34. Living alone, he became slack about his appearance.
35. There's too much slack in these ropes.
36. Demand is slack over the summer months.
37. Don't slack off in your studies.
38. He is always slack in doing his homework.
39. Business remained slack throughout the day.
40. He's been very slack in his work lately.
41. Slack the rope before trying to untie the knot.
42. After a slack period business is now picking up.
43. The tractor took up the slack and pulled the trailer out of the mud.
44. We lost because of some slack defending on our part.
45. Trade has been slack for the past year,(http://sentencedict.com/slack.html)but it is now picking up.
46. Without another contract to help pick up the slack, employees may face job losses.
47. Please slack up your speed. I can't run as fast as you!
48. Wednesdays are always slack.
49. It's natural to slack off towards the end of a hard day's work.
50. The workload can be evened out, instead of the shop having busy times and slack periods.
51. This season has been pretty slack for local hotels so far.
52. If Sue gets a job, Mick will have to take up the slack at home.
53. Hey, cut me some slack, man, I'm only a few bucks short.
54. Slack defending by Real Madrid allowed Manchester United to score.
55. As major airlines give up less-traveled routes, smaller planes are picking up the slack.
56. She knew she had been very slack in her church attendance recently.
57. We took up the slack and then pulled as hard as we could.
58. The doctor advised Facer to slack up for few days[sentencedict.com], as his lifestyle was having a bad effect on his heart.
59. England gave away a goal because of their slack marking at corners.
60. Trade has been slack for the past six months, but it is now picking up.
More similar words: slacken, lack, black, flack, lackey, blacken, lacking, black out, for lack of, blackleg, blacking, jet black, blackball, black hand, black hole, in the black, black list, black sheep, blackbody, blackface, blackmail, blacklist, blackness, lacklustre, blacksmith, lackluster, a black sheep, blackberry, black magic, black horse.