What is the meaning of stagnate?

verb

• Stand still.
  • usage: "Industry will stagnate if we do not stimulate our economy"
• Cause to stagnate.
  • usage: "There are marshes that stagnate the waters"
• Cease to flow; stand without moving.
  • usage: "Stagnating waters"; "blood stagnates in the capillaries"
• Be idle; exist in a changeless situation.
  • usage: "The old man sat and stagnated on his porch"; "He slugged in bed all morning"
  • synonyms: idle, laze, slug