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1.
When a friend or spouse is supposed to help you with directions but, instead, constantly makes negative comments about your driving.
My wife was the nagigator on our trip to the beach.
by tswift56 July 06, 2009
 
2.
When the co-pilot in a car is very annoying in the way in which they give directions.
person in passenger seat: Make a u-turn in 500 feet, and then take a left, and don't speed, you're going way too fast! Didn't you see that sign? Damn, you missed the turn, what's wrong with you?!

driver: Jeez, stop being such a nagigator..
by monkeyshort January 06, 2010