What is the meaning of slow down?

verb

• Lose velocity; move more slowly.
  • usage: "The car decelerated"
  • synonyms: decelerate, slow, slow up, retard
• Become slow or slower.
  • usage: "Production slowed"
  • synonyms: slow, slow up, slack, slacken
• Cause to proceed more slowly.
  • usage: "The illness slowed him down"
  • synonyms: slow, slow up
• Reduce the speed of.
  • usage: "He slowed down the car"
  • synonyms: decelerate
• Become less tense, rest, or take one's ease.
  • usage: "He relaxed in the hot tub"; "Let's all relax after a hard day's work"
  • synonyms: relax, loosen up, unbend, unwind, decompress