The word "pestilentious" may seem like a daunting spelling challenge, but with a little guidance from phonetics, it can be tackled with ease. The correct spelling is /pɛstɪˈlɛnʃəs/ (pes-ti-len-shuh s). The first syllable "pes" is pronounced like "pea" and the second syllable "ti" sounds like "tee". The "len" sounds like "lent" and the last syllable "shus" rhymes with "lush". The word refers to something causing harm or destruction, particularly in a contagious or infectious manner.