The Collaborative International Dictionary of English v.0.48:

Truck \Truck\, n. [L. trochus an iron hoop, Gr. ? a wheel, fr. ?
   to run. See Trochee, and cf. Truckle, v. i.]
   1. A small wheel, as of a vehicle; specifically (Ord.), a
      small strong wheel, as of wood or iron, for a gun
      carriage.
      [1913 Webster]

   2. A low, wheeled vehicle or barrow for carrying goods,
      stone, and other heavy articles.
      [1913 Webster]

            Goods were conveyed about the town almost
            exclusively in trucks drawn by dogs.  --Macaulay.
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   3. (Railroad Mach.) A swiveling carriage, consisting of a
      frame with one or more pairs of wheels and the necessary
      boxes, springs, etc., to carry and guide one end of a
      locomotive or a car; -- sometimes called bogie in England.
      Trucks usually have four or six wheels.
      [1913 Webster]

   4. (Naut.)
      (a) A small wooden cap at the summit of a flagstaff or a
          masthead, having holes in it for reeving halyards
          through.
      (b) A small piece of wood, usually cylindrical or
          disk-shaped, used for various purposes.
          [1913 Webster]

   5. A freight car. [Eng.]
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   6. A frame on low wheels or rollers; -- used for various
      purposes, as for a movable support for heavy bodies.
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   7. a motorized vehicle larger than an automobile with a
      compartment in front for the driver, behind which is a
      separate compartment for freight; esp.
      (a) such a vehicle with an inflexible body.
      (b) A vehicle with a short body and a support for
          attaching a trailer; -- also called a tractor[4].
      (c) the combination of tractor and trailer, also called a
          tractor-trailer (a form of articulated vehicle); it
          is a common form of truck, and is used primarily for
          hauling freight on a highway.
      (d) a tractor with more than one trailer attached in a
          series. In Australia, often referred to as a road
          train.
          [PJC]