The word "Coistril" is a rare and unusual term that refers to a type of small fish. The spelling of this word can be explained using the International Phonetic Alphabet (IPA), which uses symbols to represent sounds in language. In IPA, "Coistril" is spelled as /ˈkɔɪstrəl/, with the stress on the first syllable. This pronunciation guide indicates that the word begins with a short "oi" sound, followed by an "s" sound, and ends with a short "ul" sound.