When used in a sexual context it refers to the use of a blade to enhance a sexual experience. Knife play may be used in a variety of ways depending on the individuals sexual preference. It may range from simply showing the knife to instill fear, sensually running the knife along the partner possibly creating light cuts to heighten sensitivity and excitement, to even heavy pain inflicting gashes that cause permanent scarring.
> I exposed her to a form of knife play that bettered our sex life indefinitely.