Top definition
A zipper merge happens when motorists use both lanes of traffic all the way to a defined merge area, and then alternate in "zipper" fashion into the open lane. By doing it this way, both lanes are used right up until the end, which advocates like New think is a more efficient use of road space.
1st Motorist: "Zipper merging is best for slow heavy traffic. If traffic is light, early merging is fine."
2nd Motorist: "Only problem with zipper merge are the idiots who will not let you merge in front of them so they pull up tight to the car in front of them. They do this even if you try to merge early. I typically will merge at the first available open space."
by humblepiece May 23, 2015
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When the entering cars merge one by one into each space between the cars already on the road, like the notches on a zipper.

First used by Jon Stewart on The Daily Show on 8/25/10.
Jon Stewart: The hallmark of civilization is the every other car merge - the zipper merge - at tunnels.
by selenology September 06, 2010
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