tow·boat /ˈtoˌbot/
  拖船
  Tow·boat n.
  1. A vessel constructed for being towed, as a canal boat.
  2. A steamer used for towing other vessels; a tug.
  ◄ ►
  towboat
       n : a powerful small boat designed to pull or push larger ships
           [syn: tugboat, tug, tower]