Impact play is a human sexual practice in which one person is struck (usually repeatedly) by another person for the gratification of either or both parties which may or may not be sexual in nature. It is considered a form of BDSM.
There are a number of activities that qualify as impact play.
In erotic spanking the sub is struck on the buttocks either with the top's open hand, or a rigid implement such as a paddle, cane or riding crop. In the latter case the activity is often referred to as paddling, caning or cropping.