What is the meaning of Speaking_in_tongues?

(Protestantism) The act of speaking a language one does not know, or speaking elaborate but apparently meaningless speech, while in a trance-like state (or, supposedly, under the influence of a deity or spirits); glossolalia.

(Catholicism) The ability of speaking fluently a foreign language without prior learning or knowledge, supposedly under the influence of God; glossolalia.

present participle and gerund of speak in tongues.

Source: wiktionary.org