1. Change from a simple vowel to a diphthong
   "This vowel diphthongized in Germanic"
   - diphthongise [Brit]

Derived forms: diphthongized, diphthongizes, diphthongizing

See also: diphthong

Type of: change, shift, switch

• high-speed
• high-speed steel
• high-spirited
• high-spiritedness
• high-stepped
• high-stepping
• high-strength brass
• high-strung
• high-sudsing
• high-tech
• high-tension
• high-ticket
• high-toned
• high-top
• high-topped
• high-up
• high-velocity
• high-vitamin diet
• high-voltage
• high-warp loom
• high-water mark
• high-yield
• high-yield bond
• highball
• highball glass