The Collaborative International Dictionary of English v.0.48:

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]

WordNet (r) 3.0 (2006):

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"