fathom

fathom (http://definr.com/fathom)

     n 1: a linear unit of measurement (equal to 6 feet) for water
          depth [syn: fthm]
     2: (mining) a unit of volume (equal to 6 cubic feet) used in
        measuring bodies of ore [syn: fthm]
     v 1: come to understand [syn: penetrate, bottom]
     2: measure depths with a sounding line, as of a body of water
        [syn: sound]