| diphthongize | (v) change from a simple vowel to a diphthong, Syn. diphthongise, Example: This vowel diphthongized in Germanic |
| Diphthongize | v. t. & i. To change into a diphthong, as by affixing another vowel to a simple vowel. “The diphthongized long vowels.” H. Sweet. [ 1913 Webster ] |