https://en.wikipedia.org/wiki/Triphthong
In phonetics, a triphthong (UK: / ˈ t r ɪ f θ ɒ ŋ, ˈ t r ɪ p θ ɒ ŋ /, US: /-θ ɔː ŋ /) (from Greek τρίφθογγος, "triphthongos", literally "with three sounds," or "with three tones") is a monosyllabic vowel combination involving a quick but smooth movement of the articulator from one vowel quality to another that passes over a third. While "pure" vowels, or monophthongs ...