lock away vs shut up

lock away is not an adjective while shut up is an adjective.

Word	Noun	Adjective	Verb	Adverb
lock away	No	No	Yes	No
shut up	No	Yes	Yes	No

As verbs, lock away and shut up are synonyms defined as:

lock away and shut up: place in a place where something cannot be removed or someone cannot escape

Other synonyms of lock away include lock, lock in, lock up, put away, shut away.

lock away (adjective)	shut up (adjective)
	closely confined

lock away (verb)	shut up (verb)
place in a place where something cannot be removed or someone cannot escape	cause to be quiet or not talk
	refuse to talk or stop talking; fall silent
	place in a place where something cannot be removed or someone cannot escape