Neoplatonism n 1: a system of philosophical and theological doctrines composed of elements of Platonism and Aristotelianism and oriental mysticism; its most distinctive doctrine holds that the first principle and source of reality transcends being and thought and is naturally unknowable; "Neoplatonism was predominant in pagan Europe until the 6th century"; "Neoplatonism was a major influence on early Christian writers and on later medieval and Renaissance thought and on Islamic philosophy"
Neoplatonism \Ne`o*pla"to*nism\, n. [Neo- + Platonism.] A pantheistic eclectic school of philosophy, of which Plotinus was the chief (a. d. 205-270), and which sought to reconcile the Platonic and Aristotelian systems with Oriental theosophy. It tended to mysticism and theurgy, and was the last product of Greek philosophy. [1913 Webster]