What is the meaning of kink?

noun

• A painful muscle spasm especially in the neck or back (`rick' and `wrick' are British.
  • synonyms: crick, rick, wrick
• A sharp bend in a line produced when a line having a loop is pulled tight.
  • synonyms: twist, twirl
• A person with unusual sexual tastes.
• An eccentric idea.
• A difficulty or flaw in a plan or operation.
  • usage: "there are still a few kinks to iron out"

verb

• Curl tightly.
  • usage: "crimp hair"
  • synonyms: crimp, crape, frizzle, frizz, kink up
• Form a curl, curve, or kink.
  • usage: "the cigar smoke curled up at the ceiling"
  • synonyms: curl, curve