What is the meaning of shut up?

verb

• Refuse to talk or stop talking; fall silent.
  • usage: "The children shut up when their father approached"
  • synonyms: close up, clam up, dummy up, belt up, button up, be quiet, keep mum
• Place in a place where something cannot be removed or someone cannot escape.
  • usage: "The parents locked her daughter up for the weekend"; "She locked her jewels in the safe"
  • synonyms: lock in, lock away, lock, put away, shut away, lock up
• Cause to be quiet or not talk.
  • usage: "Please silence the children in the church"
  • synonyms: hush, quieten, silence, still, hush up

adjective

• Closely confined.
  • synonyms: pent