(countable) A valley, or small, shallow dell.

(mining) Small coal; coal dust.

(rail transport) A temporary speed restriction where track maintenance or engineering work is being carried out at a particular place.

To slacken. / (obsolete) To mitigate; to reduce the strength of. / To lose cohesion or solidity by a chemical combination with water; to slake.

(normally said of a rope) Lax; not tense; not firmly extended. / Weak; not holding fast. / Moderately warm. / Moderate in speed. / Lacking diligence or care; not earnest or eager.

Slackly.

(uncountable) The part of anything that hangs loose, having no strain upon it. / (countable) A tidal marsh or shallow that periodically fills and drains.

simple past tense and past participle of slack

present participle of slack

Third-person singular simple present indicative form of slack