tongue-tied vs incoherent

tongue-tied and incoherent both are adjectives.

Word	Noun	Adjective	Verb	Adverb
tongue-tied	No	Yes	No	No
incoherent	No	Yes	No	No

As adjectives, tongue-tied and incoherent are synonyms defined as:

tongue-tied and incoherent: unable to express yourself clearly or fluently

tongue-tied (adjective)	incoherent (adjective)
unable to express yourself clearly or fluently	without logical or meaningful connection
	(physics) of waves having no stable definite or stable phase relation
	unable to express yourself clearly or fluently