{ Slack (?), Slack″en (?), } v. i. [imp. & p. p.Slacked (?), Slackened (�); p. pr. & vb. n.Slacking, Slackening.] [See Slack, a.] 1. To become slack; to be made less tense, firm, or rigid; to decrease in tension; as, a wet cord slackens in dry weather.
2. To be remiss or backward; to be negligent.
3. To lose cohesion or solidity by a chemical combination with water; to slake; as, lime slacks.
4. To abate; to become less violent.
Whence these raging fires
Will slacken, if his breath stir not their flames. Milton.
5. To lose rapidity; to become more slow; as, a current of water slackens.
6. To languish; to fail; to flag.
7. To end; to cease; to desist; to slake.
That through your death your lineage should slack. Chaucer.
They will not of that firste purpose slack. Chaucer.