Diphthongize

v. t. & i.

1.

To change into a diphthong, as by affixing another vowel to a simple vowel.

Verb

1.

diphthongize - change from a simple vowel to a diphthong; "This vowel diphthongized in Germanic" Synonyms: diphthongise

break, change, diphthong, diphthongise, shift, switch