diphthongize

[dif-thawng-ahyz, -gahyz, -thong-, dip-] /ˈdɪf θɔŋˌaɪz, -ˌgaɪz, -θɒŋ-, ˈdɪp-/
verb (used with object), diphthongized, diphthongizing.
1.
to change into or pronounce as a diphthong.
verb (used without object), diphthongized, diphthongizing.
2.
to become a diphthong.
Also, especially British, diphthongise.
Origin
1865-70; diphthong + -ize
Related forms
diphthongization, noun
British Dictionary definitions for diphthongize

diphthongize

/ˈdɪfθɒŋˌaɪz; -ˌɡaɪz; ˈdɪp-/
verb
1.
(often passive) to make (a simple vowel) into a diphthong
Derived Forms
diphthongization, diphthongisation, noun