slack vs watershed

slack

noun
  • A tidal marsh or shallow that periodically fills and drains. 

  • Unconditional listening attention given by client to patient. 

  • A temporary speed restriction where track maintenance or engineering work is being carried out at a particular place. 

  • The part of anything that hangs loose, having no strain upon it. 

  • Small coal; coal dust. 

  • A valley, or small, shallow dell. 

adj
  • Moderately warm. 

  • Vulgar; sexually explicit, especially in dancehall music. 

  • Not active or busy, successful, or violent. 

  • Excess; surplus to requirements. 

  • Lax; not tense; not firmly extended. 

  • Lacking diligence or care; not earnest or eager. 

  • Lax. 

  • Moderate in speed. 

  • Weak; not holding fast. 

adv
  • Slackly. 

verb
  • To slacken. 

  • To lose cohesion or solidity by a chemical combination with water; to slake. 

watershed

noun
  • A region of land within which water flows down into a specified body, such as a river, lake, sea, or ocean; a drainage basin. 

  • The topographical boundary dividing two adjacent catchment basins, such as a ridge or a crest. 

  • The time after which material of more adult nature (violence, swear words, sex) may be broadcast on television or radio, either one laid down by law or one contrived from convention (e.g. when children are not watching) 

  • A critical point marking a change in course or development. 

adj
  • Serving to mark a significant development, change in direction, etc. 

How often have the words slack and watershed occurred in a corpus of books? (source: Google Ngram Viewer )