Definition of "slacken"

slacken

/ˈslæ.kən/

verb
third-person singular simple present slackens, present participle slackening, simple past and past participle slackened
1. (intransitive) To gradually decrease in intensity or tautness; to become slack.
  Quotations
  He seemed tired, and the Rat let him rest unquestioned, understanding something of what was in his thoughts; knowing, too, the value all animals attach at times to mere silent companionship, when the weary muscles slacken and the mind marks time.
  1908 October, Kenneth Grahame, The Wind in the Willows, New York, N.Y.: Charles Scribner’s Sons
  The action moves at lightening [sic] pace, never slackening for a moment.
  1984 April 28, Bill Kreidler, “Farcical Improbability”, in Gay Community News, page 14
2. (transitive) To make slack, less taut, or less intense.
  Quotations
  During this interlude, Warwick, though he had slackened his pace measurably, had so nearly closed the gap between himself and them as to hear the old woman say, with the dulcet negro intonation: […]
  1900, Charles W[addell] Chesnutt, chapter I, in The House Behind the Cedars, Boston, Mass., New York, N.Y.: Houghton, Mifflin and Company […]
  Elk slackened the rope so he could walk farther away, and together they went awkwardly up the trail toward the grassy little flat […]
  1986, Mari Sandoz, The Horsecatcher
3. To deprive of cohesion by combining chemically with water; to slake.