Definition: A jumper is a removable wire or small plastic or metal plug whose absence or placement on a piece of hardware determines how the hardware is to be configured.
For example, if a jumper on a hard drive is in "Position A" (I made this up), it may mean that the hard drive is to be the master hard drive on the system. If the jumper is in "Position B" it may mean that the hard drive is to be the slave hard drive in the computer.
Jumpers have all but replaced an older hardware configuration mechanism called a DIP switch. Even jumpers are rare on most newer hardware today.
Examples:
"The second hard drive I put it my computer didn't work but then I realized that I had set the jumper setting incorrectly."
