The expression "clap on" refers to the sound-activated switches that turn lights and other devices on and off by clapping one's hands. While this term has become commonly associated with the popular "Clapper" device, there are plenty of other phrases that can be used to describe this technology. Possible synonyms include "clap-activated," "hand-controlled," "sound-sensitive," or "acoustic-switched." There are also variations of the clapping-based phrase, such as "slap on" or "tap on." Regardless of the exact terminology used, these types of switches offer a convenient and hands-free way to control devices in the home.