potholing

Concise Oxford English Dictionary © 2008 Oxford University Press:
pothole/ˈpɒthəʊl/

▶noun

• 1 a deep natural underground cave formed by the eroding action of water.

  ■ a deep circular hole in a river bed formed by the eroding action of stones in an eddy.

• 2 a depression or hollow in a road surface caused by wear or subsidence.

• 3 N. Amer. a lake formed by a natural hollow in the ground in which water has collected.

▶verb Brit. explore underground potholes as a pastime.

– derivatives
potholed adjective,
potholer noun,
potholing noun.

– origin C19: from ME pot ‘pit’ (perh. of Scand. origin) + hole.