The bullroarer, rhombus, or turndun, is an ancient ritual musical instrument and a device historically used for communicating over greatly extended distances. It dates to the Paleolithic period, being found in Ukraine dating from 17,000 BC. Anthropologist Michael Boyd, a Bullroarer expert, documents a number found in Europe, Asia, the Indian sub-continent, Africa, the Americas, and Australia.

Along with the didgeridoo, it was a prominent musical technology among the Australian Aborigines, used in initiation ceremonies and in burials to ward off evil spirits, bad tidings, and especially women and children. Bullroarers are considered secret men's business by some Aboriginal tribal groups, and hence forbidden for women, children, non-initiated men, or outsiders to even hear. Anyone caught breaching the imposed secrecy was to be punished by death.

Paddy Bush played a bullroarer on the track The Dreaming.