The spelling of the word "burbliest" can be explained using IPA (International Phonetic Alphabet) transcription. It is pronounced as /ˈbɜː.bli.ɪst/ which means the word has two syllables with emphasis on the first syllable "bur" and ends with "-li-est". "Bur" is spelled with "b-u-r" and pronounced as /bɜː/. "Burbliest" is the superlative form of "burble" which means to make a continuous murmuring sound. Thus, "burbliest" means something that makes the most murmuring sounds.