1. An incomprehensible speech in an imaginary language, sometimes occurring in a trance state, an episode of religious ecstasy, or schizophrenia; speaking in tongues.
2. The ability or phenomenon of uttering words or sounds of a language unknown to the speaker; especially, as an expression of religious ecstasy.

From the Greek, "γλώσσα" (glossa), "tongue" and "λαλώ" (lalô), "to speak"; consisting of the utterance of what appears (to the casual listener) either as an unknown foreign language (xenoglossia), meaningless syllables, or an utterance of an unknown mystical language. The utterances sometimes occur as part of religious worship (religious glossolalia).

Profuse and often emotionally charged speech that mimics coherent speech but is usually unintelligible to the listener and is uttered in some state of religious ecstasy and in some schizophrenic conditions.

When spoken by schizophrenics, glossolalia is recognized as gibberish. In charismatic Christian communities glossolalia is sacred and referred to as "speaking in tongues" or having "the gift of tongues."

In Acts of the Apostles, tongues of fire are described as alighting on the Apostles, filling them with the Holy Spirit. Allegedly, this allowed the Apostles to speak in their own language but be understood by foreigners from several nations.

Glossolalics, on the other hand, speak in a foreign language and are typically not understood by anyone.