Source : Webster's Revised Unabridged Dictionary (1913)

Utmost \Ut"most`\, n.
   The most that can be; the farthest limit; the greatest power,
   degree, or effort; as, he has done his utmost; try your
   utmost.

         We have tried the utmost of our friends. --Shak.

Utmost \Ut"most`\, a. [OE. utmeste, utemest, AS. ?temest, a
   superlative fr. ?te out. ????. See {Out}, and cf.
   {Aftermost}, {Outmost}, {Uttermost}.]
   1. Situated at the farthest point or extremity; farthest out;
      most distant; extreme; as, the utmost limits of the land;
      the utmost extent of human knowledge. --Spenser.

            We coasted within two leagues of Antibes, which is
            the utmost town in France.            --Evelyn.

            Betwixt two thieves I spend my utmost breath.
                                                  --Herbert.

   2. Being in the greatest or highest degree, quantity, number,
      or the like; greatest; as, the utmost assiduity; the
      utmost harmony; the utmost misery or happiness.

            He shall answer . . . to his utmost peril. --Shak.

            Six or seven thousand is their utmost power. --Shak.

Source : WordNet®

utmost
     adj 1: of the greatest possible degree or extent or intensity;
            "extreme cold"; "extreme caution"; "extreme pleasure";
            "utmost contempt"; "to the utmost degree"; "in the
            uttermost distress" [syn: {extreme}, {utmost(a)}, {uttermost(a)}]
     2: highest in extent or degree; "to the last measure of human
        endurance"; "whether they were accomplices in the last
        degree or a lesser one was...to be determined
        individually" [syn: {last}]
     3: (comparatives of `far') most remote in space or time or
        order; "had traveled to the farthest frontier"; "don't go
        beyond the farthermost (or furthermost) tree"; "explored
        the furthest reaches of space"; "the utmost tip of the
        peninsula" [syn: {farthermost}, {farthest}, {furthermost},
         {furthest}, {uttermost}]
     n : the greatest possible degree; "he tried his utmost" [syn: {uttermost},
          {maximum}, {level best}]