noun.
A nail with a wide head, traditionally used in the construction and ornamentation of wooden doors.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
noun.
a nail with a large head; formerly used to decorate doors
Word Usage
"Snow (UID#1832) on August 24th, 2009 at 5: 05 pm you clearly dont have the IQ of a doornail. a doornail is far smarter than you and it has a purpose."