What is the meaning of tightening?

noun

• The act of making something tighter.
  • usage: "the tightening of economic controls"

verb

• Make tight or tighter.
  • usage: "Tighten the wire"
  • synonyms: tighten, fasten
• Become tight or tighter.
  • usage: "The rope tightened"
  • synonyms: tighten
• Restrict.
  • usage: "Tighten the rules"; "stiffen the regulations"
  • synonyms: stiffen, tighten, tighten up, constrain
• Narrow or limit.
  • usage: "reduce the influx of foreigners"
  • synonyms: reduce, tighten