Definition: To prick a pie crust with a fork before baking. This lets the steam escape so the pie crust doesn't puff up in the often. Usually used when blind baking a pie crust before filling. There are docking tools you can buy that will dock a crust before you put it in the pie pan.
Examples: Dock the pie crust before baking so it will lay flat and will not puff up.
You can "dock" a pastry by pricking it with a fork, or using a tool specifically made for this task.
Unless you bake pies every day, a fork will be just fine.
The holes made by the fork or docking tool will fill up when the pastry bakes, so you don't have to worry about the filling leaking through the crust to the pie pan below. Don't make the holes too big; they should be large enough so steam will escape, but not so big that you tear the pastry.