diphthongize
/ˈdɪfθɔŋaɪz/
verb
- To pronounce a simple vowel as a diphthong (a gliding vowel sound).
- When you diphthongize a vowel, your tongue moves from one position to another.
- Many American speakers diphthongize the vowel in 'price' so it sounds like 'prah-ees'.
- Linguists study how different regions diphthongize certain vowels.