Tug

n.
  1. A pull with the utmost effort, as in the athletic contest called tug of war; a supreme effort.
  2. A sort of vehicle, used for conveying timber and heavy articles.
  3. (Naut.) A small, powerful steamboat used to tow vessels; -- called also steam tug, tugboat, and towboat.
  4. A trace, or drawing strap, of a harness.
  5. (Mining.) An iron hook of a hoisting tub, to which a tackle is affixed.
    6. Tug iron ,
    an iron hook or button to which a tug or trace may be attached, as on the shaft of a wagon.