What is the meaning of subside?

verb

• Wear off or die down.
  • usage: "The pain subsided"
  • synonyms: lessen
• Sink to a lower level or form a depression.
  • usage: "the valleys subside"
• Sink down or precipitate.
  • usage: "the mud subsides when the waters become calm"
  • synonyms: settle
• Descend into or as if into some soft substance or place.
  • usage: "He sank into bed"; "She subsided into the chair"
  • synonyms: sink