The Collaborative International Dictionary of English v.0.48:

Underrun \Un`der*run"\, v. t.
   To run or pass under; especially (Naut.), to pass along and
   under, as a cable, for the purpose of taking it in, or of
   examining it.
   [1913 Webster]

   Note: The cable passes over the bows and stern of the boat
         used, while the men haul the boat along by pulling upon
         the cable. --Totten.
         [1913 Webster]

   To underrun a hose (Naut.), to lift it up at one end, then
      walk along shifting one hand after another so that the
      water will run out.

   To underrun a tackle (Naut.), to separate its parts and put
      them in order.
      [1913 Webster]