incoherent vs tongue-tied

incoherent and tongue-tied both are adjectives.

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

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

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

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