flap vs slack

flap

noun
  • Anything broad and flexible that hangs loose, or that is attached by one side or end and is easily moved. 

  • A side fin of a ray. 

  • A consonant sound made by a single muscle contraction, such as the sound /ɾ/ in the standard American English pronunciation of body. 

  • The motion of anything broad and loose, or a sound or stroke made with it. 

  • A piece of tissue incompletely detached from the body, as an intermediate stage of plastic surgery. 

  • A hinged leaf. 

  • The labia, the vulva. 

  • A hinged surface on the trailing edge of the wings of an aeroplane, used to increase lift and drag. 

  • A controversy, scandal, stir, or upset. 

verb
  • To move loosely back and forth. 

  • To move (something broad and loose) up and down. 

  • Of a resource or network destination: to be advertised as being available and then unavailable (or available by different routes) in rapid succession. 

slack

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

  • 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. 

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

  • Small coal; coal dust. 

  • A valley, or small, shallow dell. 

verb
  • To slacken. 

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

adv
  • Slackly. 

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. 

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