What is the meaning of tied up?

verb

• Secure with or as if with ropes.
  • usage: "tie down the prisoners"; "tie up the old newspapers and bring them to the recycling shed"
  • synonyms: tie down, tie up, bind, truss
• Invest so as to make unavailable for other purposes.
  • usage: "All my money is tied up in long-term investments"
  • synonyms: tie up
• Restrain from moving or operating normally.
  • usage: "Traffic is tied up for miles around the bridge where the accident occurred"
  • synonyms: tie up
• Secure in or as if in a berth or dock.
  • usage: "tie up the boat"
  • synonyms: moor, berth, tie up
• Finish the last row.
  • synonyms: tie up, bind off

adjective

• Kept occupied or engaged.
  • usage: "she's tied up at the moment and can't see you"; "the phone was tied up for almost an hour"