NOUN (3)

1. a social organization in which diversity of racial or religious or ethnic or cultural groups is tolerated;

2. the doctrine that reality consists of several basic substances or elements;

3. the practice of one person holding more than one benefice at a time;

The Collaborative International Dictionary of English v.0.48:

Pluralism \Plu"ral*ism\, n.
   1. The quality or state of being plural, or in the plural
      number.
      [1913 Webster]

   2. (Eccl.) The state of a pluralist; the holding of more than
      one ecclesiastical living at a time. [Eng.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

pluralism
    n 1: a social organization in which diversity of racial or
         religious or ethnic or cultural groups is tolerated
    2: the doctrine that reality consists of several basic
       substances or elements [ant: monism]
    3: the practice of one person holding more than one benefice at
       a time