Por`phy*ro*gen"i*tism (?), n. [LL.
porphyro genitus, fr. Gr. ?; ? purple + root of ? to be
born.] The principle of succession in royal families, especially
among the Eastern Roman emperors, by which a younger son, if born
after the accession of his father to the throne, was preferred to an
elder son who was not so born. Sir T. Palgrave.