The word "scrubbest" is not a commonly used term, as it is a non-standard variation of the verb "scrub." It derives from the irregular past tense form "scrubbed," with the addition of the superlative "-est" suffix. In IPA phonetic transcription, the word would be transcribed as /ˈskrʌbɪst/. However, it is important to note that while this word may be grammatically incorrect, it is not uncommon for non-standard variations to exist in spoken language.