(1) A security device used to shut off any other device in an emergency situation in which a normal shut down is not possible. Kill switches are commonly used on motorized devices and electronic devices. In computing, a kill switch is often called a BRS or Big Red Switch.
(2) In software, a kill switch is used by software developers for anti-piracy measures, where features of the software are “killed” or rendered useless and inaccessible to users running pirated versions of the software.