A Vowel Tetragram (VT) is a group of 4 vowels unbroken by any consonants. There are 625 different VTs (125 beginning with each of A, E, I, O, and U), ranging from AAA, AAAE through UUUO, UUU. Words which contain a VT can be called Vowel Tetragram Words (VTWs). Relatively few words in current everyday usage include a VT. AQUEOUS, QUEUE, ONOMATOPOEIA, COOEE, HAWAIIAN and SEQUOIA are perhaps the most familiar.
"Vowel Tetragrams Revisited,"
Word Ways: Vol. 36
, Article 7.
Available at: https://digitalcommons.butler.edu/wordways/vol36/iss4/7