secure

Immune to attack; incapable of being tampered with.

“a secure telephone connection”

Free from danger or risk.

“secure from harm”

“his fortune was secure”

Not likely to fail or give way.

“the lock was secure”

“a secure foundation”

Financially safe.

“a secure investment”

Free from fear or doubt; easy in mind.

“he was secure that nothing will be held against him”

Fill or close tightly with or as if with a plug.

Make certain of.

Furnish with battens.

Get by special effort.

Cause to be firmly attached.

Assure payment of.