Occurs when a work piece is thrown back toward the operator. The most common kickback woodworkers encounter is at the tablesaw. This occurs in two common scenarios: the wood being cut gets jammed between the rip fence and the blade or the wood itself closes in on the back of the blade curing the cut.
The likelihood of kickback can be dramatically reduced by using a splitter or riving knife, and making sure the rip fence is perfectly parallel with the blade. In addition, using other safety devices like featherboards and push sticks will help maintain control of the workpiece during the cut.
Here are some great links dealing with kickback and tablesaw safety:
Tablesaw Kickback – Video: Kickback in Action
Tablesaw Safety Video – Video: Tablesaw Experience
Kickback Overview – Article: Kickback