Stillson wrench

from WordNet (r) 3.0 (2006)

Stillson wrench
    n 1: a large pipe wrench with L-shaped adjustable jaws that
         tighten as pressure on the handle is increased

from The Collaborative International Dictionary of English v.0.48

Stillson wrench \Still"son wrench\
   A pipe wrench having an adjustable L-shaped jaw piece sliding
   in a sleeve that is pivoted to, and loosely embraces, the
   handle. Pressure on the handle increases the grip.
   [Webster 1913 Suppl.]