 It indicates that he is regarded as having extraordinary intelligence and mental capacity, necessary for the most serious, advanced and complex Talmudic learning and Torah study.In common terminology, an "illui" would be someone who has an extraordinarily high "IQ" as recognized from early childhood as a child prodigy by rabbis and Torah scholars who have a keen eye to recognize the qualities of excellence in budding young Torah scholars.Haredi and Hasidic Jews are very familiar with this term, and if a scholar that they are familiar with has been known to have been called an "illui" they will regard it as a great honor for that individual as well as for his family, teachers and those with whom he associates.