bull-roarer at English => English (The Britannica Concise) Of Explained:
Flat piece of wood, several inches to a foot in length, fastened at one end to a string, by which it is swung around in the air to produce a whirring or howling sound likened to those of animals or spirits. It has been observed in Australia, the Americas, and other areas where indigenous societies survive. It may symbolize totemic ancestors, or it may be believed to cause or cure sickness, warn women and children away from men's sacred ceremonies, control the weather, or promote fertility in animals and crops.
Bull-roarer at English => English (Websters 1913) Of Explained:
Bull-roarer \Bull"-roar`er\, n.
A contrivance consisting of a slat of wood tied to the end of
a thong or string, with which the slat is whirled so as to
cause an intermittent roaring noise. It is used as a toy, and
among some races in certain religious rites.