The word "quietliest" is spelled using the letter combination of "ui" to create the /kw/ sound. The IPA phonetic transcription for this word is /ˈkwaɪətlɪst/. The suffix "-liest" is added to the end of the base word "quiet" to create a superlative form, meaning "most quiet". While this word may not be frequently used in everyday conversation, it exemplifies the complexity of English spelling and the importance of understanding phonetics to correctly pronounce and spell unfamiliar words.
"Quietliest" is not a recognized English word. It appears to be an inflected form of the adjective "quiet", referring to the comparative form of "quietly". However, "quietliest" is not a common comparative form used in English. It is more usual to use "quieter" or "more quiet" as comparatives.