Stands for "Zero Insertion Force." ZIF is a type of CPU socket on a computer motherboard that allows for the simple replacement or upgrade of the processor. Processors that use a ZIF socket can easily be removed by pulling a small release lever next to the processor and lifting it out. The replacement processor is then placed in the socket and secured by pushing the lever in the opposite direction -- hence the phrase, "zero insertion force." I suppose there is some force required to push the lever, but it is significantly less than non-ZIF sockets, which require special tools to force the processor out.