Glossolalia, or speaking in tongues, is speaking rapid speech-like syllables which cannot be understood. In some cases it is part of religious practice. Some consider it as a part of a sacred language. It is a common practice amongst Pentecostal and Charismatic Christianity.
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Headline about the "Weird babel of tongues" and other behavior at Azusa Street, from a 1906 Los Angeles Times newspaper.
Glossolalia Facts for Kids. Kiddle Encyclopedia.