Omnilingual

Tom is omnilingual. He can speak every language on Earth.

Source: tatoeba (5239232)

God is, of course, omnilingual. He can understand everyone's prayers, no matter what language they're in.

Source: tatoeba (5239233)

Sir, my omnilingual Diorama having recently appeared in your useful publication, unconnected with some of the proofs that it has a just claim to such a comprehensive title, I shall now, with your permission, submit a prospectus of my universal characters contrasted with those which are most current over the Asiatic Peninsula, to the inspection of many Orientalists among your readers, very well qualified to decide impartially on the comparative merits of my scheme, at least in its application to the two indispensable languages for British India: namely, the Hindoostanee and Persian tongue.

Source: wiktionary

Because they are in some sense part of an omnilingual scholarly vocabulary, many instructors require their students to learn them and use them.

Source: wiktionary