stop up vs secure

stop up is not an adjective while secure is an adjective.

Word	Noun	Adjective	Verb	Adverb
stop up	No	No	Yes	No
secure	No	Yes	Yes	No

As verbs, stop up and secure are synonyms defined as:

Other synonyms of stop up include plug.

stop up (adjective)	secure (adjective)
	free from fear or doubt; easy in mind
	free from danger or risk
	not likely to fail or give way
	immune to attack; incapable of being tampered with
	financially safe

stop up (verb)	secure (verb)
fill or close tightly with or as if with a plug	make certain of
	cause to be firmly attached
	fill or close tightly with or as if with a plug
	furnish with battens
	get by special effort
	assure payment of