<p><strong>Adjective:</strong></p><ul><li>Not tight, taut, firm, or tense; a slack rope.</li><li>Synonyms: relaxed.</li><li>Negligent; careless; remiss: slack proofreading.</li><li>Synonyms: thoughtless, lazy, lax.</li><li>Slow, sluggish, or indolent: He is slack in answering letters.</li><li>Synonyms: listless, tardy, dilatory.</li><li>Not active or busy; dull; not brisk: the slack season in an industry.</li><li>Synonyms: quiet, idle.</li><li>Moving very slowly, as the tide, wind, or water.</li><li>Phonetics: weak; lax.</li><li>Nautical: easy.</li></ul><p><strong>Adverb:</strong></p><ul><li>In a slack manner.</li></ul><p><strong>Noun:</strong></p><ul><li>A slack condition or part.</li><li>The part of a rope, sail, or the like, that hangs loose, without strain upon it.</li><li>A decrease in activity, as in business or work: a sudden slack in output.</li><li>Synonyms: relaxation.</li><li>A period of decreased activity.</li><li>Geography: a cessation in a strong flow, as of a current at its turn.</li><li>A depression between hills, in a hillside, or in the land surface.</li><li>Prosody: (in sprung rhythm) the unaccented syllable or syllables.</li><li>British Dialect: a morass; marshy ground; a hollow or dell with soft, wet ground at the bottom.</li></ul><p><strong>Verb (used with object):</strong></p><ul><li>To be remiss in respect to (some matter, duty, right, etc.); leave undone; shirk: He slacked the most important part.</li><li>Synonyms: neglect.</li><li>To make or allow to become less active, vigorous, intense, etc.; relax (efforts, labor, speed, etc.); lessen; moderate (often followed by up).</li><li>Synonyms: slacken, reduce.</li><li>To make loose, or less tense or taut, as a rope; loosen (often followed by off or out).</li><li>To slake (lime).</li></ul><p><strong>Verb (used without object):</strong></p><ul><li>To be remiss; shirk one's duty or part.</li><li>Synonyms: malinger.</li><li>To become less active, vigorous, rapid, etc. (often followed by up): Business is slacking up.</li><li>To become less tense or taut, as a rope; to ease off.</li><li>To become slaked, as lime.</li></ul>