The word "fussest" is a variant spelling of the present tense second person singular form of the verb "fuss," which means to worry or make a big deal out of something. The phonetic transcription of "fussest" is /ˈfʌsəst/, with stress on the first syllable: "fuss-est." The "-est" ending is a suffix that marks the second person singular form in standard English verbs (-est = "you" or "thou"). While "fussest" may not be a commonly used variant, it is still a valid spelling that follows the rules of English grammar.