It is said of the word or language that contains the five vowels of Spanish. It applies in languages such as Quechua or Aymara whose original transcribed spelling used the letters /a/, /e/, /i/, /o/ and /u/, but at the end of the 20th century the use of only /a/, /i/ and /u/ became trivocal. Another use for 'pentavocalic' is to group each word with all the vowels, but there is no criterion on how to include them, since according to some authors those with repeated vowels (which counts more than 5), those with stressed vowels (because they are another character), those that contain the /u/ in the digraph /qu/ (because it does not sound), should not be accepted. those that have /y/ instead of /i/ (even if they do sound the same) , . . . My only objection is the etymological sloppiness, since penta- ("five") is a prefix of Greek origin while vowel is a Latin word; But it's true that 'quinquivocalic' sounds ugly. See panvocalic.