Definition of "triphthong" []

• A compound vowel sound resulting from the succession of three simple ones and functioning as a unit. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "A triphthong is a sequence of three vowels making up one syllable."
• "A triphthong is the union of _three_ vowels pronounced in like manner; as, _eau_ in beau, _iew_ in view."
• "The union of three vowels in one sound is called a triphthong; as iew in view."