Source : Webster's Revised Unabridged Dictionary (1913)

Nasalize \Na"sal*ize\, v. t. [imp. & p. p. {Nasalized}; p. pr. &
   vb. n. {Nasalizing}.]
   To render nasal, as sound; to insert a nasal or sound in.

Nasalize \Na"sal*ize\, v. t.
   To utter words or letters with a nasal sound; to speak
   through the nose.

Source : WordNet®

nasalize
     v 1: speak nasally or through the noze; "In this part of the
          country, people tend to nasalize" [syn: {nasalise}]
     2: pronounce with a lowered velum; "She nasalizes all her
        vowels" [syn: {nasalise}]