tied up (Adjective) — Kept occupied or engaged. ex. "she's tied up at the moment and can't see you" ex. "the phone was tied up for almost an hour"
tied up (Verb) — Secure with (or as if with) ropes in order to prevent movement or escape. ex. "tie up the old newspapers and bring them to the recycling shed"
tied up (Verb) — Invest so as to make unavailable for other purposes. ex. "All my money is tied up in long-term investments"
tied up (Verb) — Restrain from moving or operating normally. ex. "Traffic is tied up for miles around the bridge where the accident occurred"
tied up (Verb) — Secure in or as if in a berth or dock. ex. "tie up the boat"
tied up (Verb) — (knitting) finish the last row.