The Collaborative International Dictionary of English v.0.48:

Crownwork \Crown"work`\ (-w?rk`), n. (Fort.)
   A work consisting of two or more bastioned fronts, with their
   outworks, covering an enceinte, a bridgehead, etc., and
   connected by wings with the main work or the river bank.
   [1913 Webster]

WordNet (r) 3.0 (2006):

crownwork
    n 1: (dentistry) dental appliance consisting of an artificial
         crown for a broken or decayed tooth; "tomorrow my dentist
         will fit me for a crown" [syn: crown, crownwork,
         jacket, jacket crown, cap]