secure vs stop up

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

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

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

Other synonyms of secure include plug.

secure (adjective)	stop up (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

secure (verb)	stop up (verb)
make certain of	fill or close tightly with or as if with a plug
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