Source : Webster's Revised Unabridged Dictionary (1913)

Farthermost \Far"ther*most`\, a.
   Most remote; farthest.

Source : WordNet®

farthermost
     adj : (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: {farthest}, {furthermost},
           {furthest}, {utmost}, {uttermost}]