propreantepenult UK /ˌpɹəʊpɹiːˌantɪpɪˈnʌlt/US /ˌpɹoʊpɹiˌantiˈpiˌnʌlt/ noun1 •(rare) The last syllable but four; the fifth-to-last syllable (of a word or other utterance); a word’s or other utterance’s propreantepenultimate syllable.The word dis·ín·te·res·ted·ly is stressed on the propreantepenult.