Definition of "doornail" [door•nail]

• A large-headed nail. (noun)
• Dead as a doornail Undoubtedly dead. (idiom)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "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."
• "One sure sign that the Senate health care bill is dead as a doornail is the inevitable appearance of the anonymously-sourced, finger-pointing articles."
• "Alan SparrowElmswell, Suffolk• Green shoots of economic recovery, deader than a doornail, Catford, 24 April."