Definition of nasalize in US English:

nasalize

(British nasalise)

verb

[with object]
  • Pronounce or utter (a speech sound) with the breath resonating in the nose.

    ‘this sound and sensation should be memorized so that the singer can learn to consistently avoid nasalizing vowels’
    • ‘Try saying ‘cromps,’ while nasalizing the m a little, like in French.’
    • ‘The first small problem with the Reuters article is that the usual spelling for the language is ‘Pirahã’, with a tilde over the final /a/, indicating that the vowel is nasalized.’
    • ‘French is essentially a language that elides everything that doesn't get out of the way fast enough, and nasalises everything else.’
    • ‘In speech, hard ‘r’ frequently gets nasalized, in the same way as ‘k’ becomes aspirated in the American throat.’
    • ‘Also, the nasal cavity can be closed thus preventing vowels from being nasalised and thus increasing their comprehensibility.’
    • ‘But after, for example, verbs ending in ‘a’, ‘en’ gloms onto the verb and turns the final ‘a’ into an ‘eh’ sound, creating a long, nasalized ‘eh’.’
    • ‘In southern England, the vowel is nasalized and long.’

Pronunciation

nasalize

/ˈnāzəˌlīz//ˈneɪzəˌlaɪz/