uttermost vs boundary

uttermost and boundary both are nouns.

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

As nouns, boundary is a hypernym of uttermost; that is, boundary is a word with a broader meaning than uttermost:

Other hypernyms of uttermost include bound, limit.

uttermost (noun)	boundary (noun)
the greatest possible degree	the greatest possible degree of something
	the line or plane indicating the limit or extent of something
	a line determining the limits of an area

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