uttermost vs furthermost

uttermost is a noun but furthermost is not a noun.

Word	Noun	Adjective	Verb	Adverb
uttermost	Yes	Yes	No	No
furthermost	No	Yes	No	No

As adjectives, uttermost and furthermost are synonyms defined as:

uttermost and furthermost: (comparatives of `far') most remote in space or time or order

Other synonyms of uttermost include farthermost, farthest, furthest, utmost.

uttermost (noun)	furthermost (noun)
the greatest possible degree

uttermost (adjective)	furthermost (adjective)
(comparatives of `far') most remote in space or time or order	(comparatives of `far') most remote in space or time or order
of the greatest possible degree or extent or intensity