Naviguessor 

The person sitting shot gun in a vehicle who is in charge of relaying information to the driver about the vehicles course, but has no idea how to get to the destination or read a map.

John the naviguessor made Todd the driver do three U-turns before they got to the mall.

Naviguessor by w0rdy August 8, 2009

naviguesser 

noun - A person similar to a navigator, but who has either no idea of how to get to where one is going or only a vague idea, and they therefore attempt to give directions that are very bad or completely wrong.

Can also be used as a verb - navigeussing

Matt and Jim were trying to drive from LA to Ventura, but end up heading towards Bakersfield:

Jim "Did we miss the turn of for the 101? I thought you were paying attention to the signs."

Matt "Um, I thought we take the 5 all the way up.

Jim "Good job naviguesser, can't you use mapquest?"

naviguesser by ahack March 4, 2009

naviguessing 

The art of navigating when you have no idea what you are doing and know full well that your directions will likely result in going the wrong way.

I'm naviguessing that we should take this next left turn.

naviguessing by Boondogglers Anonymous August 28, 2013