FURTHERMOST
farthermost, farthest, furthermost, furthest, utmost, uttermost
(adjective) (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”
Source: WordNet® 3.1
Etymology
Adjective
furthermost
superlative form of far: most far; most far; farthest.
Source: Wiktionary
Fur"ther*most", a.
Definition: Most remote; furthest.
Source: Webster’s Unabridged Dictionary 1913 Edition