The spelling of the word "opisthure" can be quite confusing, as it is not a commonly used word. However, its pronunciation can be clarified using the International Phonetic Alphabet (IPA). The first syllable is pronounced as "oh-pis" with a long "o" sound and a short "i" sound. The second syllable is pronounced as "thur" with a short "u" sound and a rolled "r". Overall, the correct pronunciation is /oʊˈpɪstʊr/.