Literally what happens when a person outside the car tries to open a locked car door just as the person INSIDE the car is pressing the "unlock" button. The common result is that the door becomes temporarily jammed and must be opened from the inside. Both people generally blame each other.

Figurtively, it is when two people try to solve a problem at the same time in divergent ways, but their separate actions cancel each other out and cause the problem to remain frozen.
The Kurds, Sunnis, and Shiites handlelocked the country of Iraq when they tried separate ways to solve their country's problems.
by Steve Rutledge February 22, 2008
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