The Collaborative International Dictionary of English v.0.48:

Pluralize \Plu"ral*ize\, v. t. [imp. & p. p. Pluralized; p.
   pr. & vb. n. Pluralizing.]
   1. To make plural by using the plural termination; to
      attribute plurality to; to express in the plural form.
      [1913 Webster]

   2. To multiply; to make manifold. [R.]
      [1913 Webster]