The Collaborative International Dictionary of English v.0.48:

Popularize \Pop"u*lar*ize\, v. t. [imp. & p. p. Popularized;
   p. pr. & vb. n. Popularizing.] [Cf. F. populariser.]
   To make popular; to make suitable or acceptable to the common
   people; to make generally known; as, to popularize
   philosophy. "The popularizing of religious teaching."
   --Milman.
   [1913 Webster]

WordNet (r) 3.0 (2006):

popularize
    v 1: cater to popular taste to make popular and present to the
         general public; bring into general or common use; "They
         popularized coffee in Washington State"; "Relativity Theory
         was vulgarized by these authors" [syn: popularize,
         popularise, vulgarize, vulgarise, generalize,
         generalise]
    2: make understandable to the general public; "Carl Sagan
       popularized cosmology in his books" [syn: popularize,
       popularise]

Moby Thesaurus II by Grady Ward, 1.0:

42 Moby Thesaurus words for "popularize":
   account for, allegorize, clarify, clear up, coarsen, crack,
   decipher, demonstrate, demythologize, elucidate, enlighten,
   euhemerize, exemplify, explain, explain away, explicate, exposit,
   expound, get across, get over, give reason for, give the meaning,
   illuminate, illustrate, make clear, make it clear, make plain,
   put across, put over, rationalize, shed light upon, show, show how,
   show the way, simplify, solve, spell out, throw light upon, unfold,
   unlock, unravel, vulgarize