Source : Webster's Revised Unabridged Dictionary (1913)

Monism \Mon"ism\, n. [From Gr. ? single.]
   1. (Metaph.) That doctrine which refers all phenomena to a
      single ultimate constituent or agent; -- the opposite of
      dualism.

   Note: The doctrine has been held in three generic forms:
         matter and its phenomena have been explained as a
         modification of mind, involving an idealistic monism;
         or mind has been explained by and resolved into matter,
         giving a materialistic monism; or, thirdly, matter,
         mind, and their phenomena have been held to be
         manifestations or modifications of some one substance,
         like the substance of Spinoza, or a supposed unknown
         something of some evolutionists, which is capable of an
         objective and subjective aspect.

   2. (Biol.) See {Monogenesis}, 1.

Monism \Mon"ism\, n.
   The doctrine that the universe is an organized unitary being
   or total self-inclusive structure.

         Monism means that the whole of reality, i.e.,
         everything that is, constitutes one inseparable and
         indicisible entirety. Monism accordingly is a unitary
         conception of the world. It always bears in mind that
         our words are abstracts representing parts or features
         of the One and All, and not separate existences. Not
         only are matter and mind, soul and body, abstracts, but
         also such scientific terms as atoms and molecules, and
         also religious terms such as God and world. --Paul
                                                  Carus.

Source : WordNet®

monism
     n : the doctrine that reality consists of a single basic
         substance or element