Merriam-Webster Collegiate Dictionary - utmost

 I. adjective  Etymology: Middle English, alteration of utmest, from Old English utmest, superlative adjective, from ut out, adverb — more at out  Date: before 12th century  1. situated at the farthest or most distant point ; extreme the ~ point of the earth — John Hunt  2. of the greatest or highest degree, quantity, number, or amount a matter of ~ concern  II. noun  Date: before 12th century  1. the most possible ; the extreme limit ; the highest attainable point or degree the ~ in reliability  2. the highest, greatest, or best of one's abilities, powers, and resources will do our ~ to help