utter vs speak

utter is an adjective but speak is not an adjective.

Word	Noun	Adjective	Verb	Adverb
utter	No	Yes	Yes	No
speak	No	No	Yes	No

As verbs, utter and speak are synonyms defined as:

Other synonyms of utter include mouth, talk, verbalise, verbalize.

utter (adjective)	speak (adjective)
complete and absolute
without qualification; used informally as (often pejorative) intensifiers

utter (verb)	speak (verb)
express in speech	express in speech
articulate; either verbally or with a cry, shout, or noise	exchange thoughts; talk with
express audibly; utter sounds (not necessarily words)	use language
put into circulation	give a speech to
	make a characteristic or natural sound