GUGLIELMO il BRETONE. – Franciscan, theologian, and biblical scholar, who lived in the 13th century and is mentioned in his chronicle by fra Salimbene da Parma, who met him at Lyon in 1248 (cf. Cronica, ed. F. Bernini, I, Bari 1942, pp. 333–34).
He is the author of a highly esteemed work, used and copied in the Middle Ages, which is cited under various titles: Summa difficilium cocobulorum Bibliae ex glossis sanctorum, or Summa, or Vocabularium, or Liber Britonis. Ever diligent in seeking the true meaning of words, so as better to understand their value and force, he presents, amid historical, physical, and etymological dissertations, valuable and interesting points of view. He also wrote: Postillae super prologos Biblias, and Correctio seu castigatio quorumdam locorum S. Scripturae.