Utterest
Pronunciation : Ut"ter*est
Part of Speech : obs.
Definition : Defn: Uttermost. To the utterest proof of her courage. Chaucer.
superl. of Utter.
Source : Webster's Unabridged Dictionary, 1913
Merriam-Webster's Everyday Language Reference Set: Includes: The Merriam-Webster Dictionary, The Merriam-Webster Thesaurus, and The Merriam-Webster Vocabulary Builder