univocal
A word having only one meaning.
A document containing instances of only one vowel.
The univocal is by no means the preserve of the nineteenth century. Georges Perec's 1972 novella Les revenentes complemented his earlier lipogrammatic work by being a univocalic piece in which the letter e is the only vowel used.
Where it comes from
From Late Latin ūnivocus + -al. By surface analysis, uni- + vocal.
Adapted from the Wiktionary entry univocal (CC BY-SA 4.0).