phrases, sayings, idioms and expressions at

Dead reckoning

Posted by ESC on February 24, 2000

In Reply to: Dead reckoning posted by jeff waite on February 23, 2000

: A phrase used in navigation when the pilot/captain is not using any navigation aids other than a map, clock, compass and speed indications, as compared to more modern devises like radio beacons or now GPS systems, etc.
: Does any one know the origin?

"Dead" as an adverb means "absolutely, completely," according to "The Barnhart Concise Dictionary of Etymology" by Robert K. Barnhart. That's the only clue I could find.