'Doornail' definitions:

Definition of 'doornail'

(from WordNet)
noun
A nail with a large head; formerly used to decorate doors

Definition of 'Doornail'

From: GCIDE
  • Doornail \Door"nail`\ (d[=o]r"n[=a]l`), n. The nail or knob on which in ancient doors the knocker struck; -- hence the old saying, "As dead as a doornail." [1913 Webster]