to be/get tied up
Tom: What happened to you yesterday? You were supposed to go out to dinner with me and Jeff?
Jerry: Well, I got tied up at work and I couldn't leave my office until it was like 10pm.
Tom: Oh, we were worried. Next time just call us and let us know if something comes up.
Sara: Do you want to go to the beach with us this Saturday?
Jill: Oh, I would love to, but my friend is moving and I'm going to be tied up helping her pack and move.
Sara: Alright maybe next time!
Meaning: to be/get tied up is an American idiom that means someone is busy doing something. When this idiom is followed by a very phrase it must be followed by a gerund (see context #2 above).
This idiom was taken from LSI's book Speaking Savvy, which is used to teach the Level 5 Speaking class at LSI schools. For more information please visit www.languagesystems.com