The word "Altisonous" is a rare adjective that describes something that's high-pitched or sibilant. The pronunciation of this word is marked by the presence of certain phonemes that require a unique spelling. The IPA phonetic transcription for "Altisonous" is /æltɪsənəs/, which represents the different vowel and consonant sounds in the word. The "a" in the first syllable is pronounced with the same sound as "all," while the "i" and "o" sounds in the second syllable are stress syllables that make the word sound sharp and vibrant.