The word "most codicillary" is not a common one, but it refers to something that is related to codicils, which are supplements or additions made to a will. The spelling of the word can be explained using IPA phonetic transcription as /moʊst kɑːdɪsɪləri/. The initial "mo" is pronounced like "mow", followed by the "st" sound. The stressed syllable is "codi", pronounced like "kaa-di", followed by "sil" and "ary". All in all, the spelling and pronunciation of "most codicillary" may pose a challenge for those unfamiliar with legal jargon.