Able to be submerged.
A small nonmilitary, non-nuclear submarine for exploration.
A term used primarily by some navies for nuclear submarines, termed "true submersibles", because they cannot retroactively declare that their non-nuclear submarines should be called by a different name.
A very small "baby" submarine designed for specific localized missions, usually while tethered to a submarine or ship for life support and communications. Slang synonyms: midget-submarine, anchor.
A retroactive term used for non-nuclear submarines; nuclear submarines are termed "true submarines".
Below ground, under the earth, underground.
Secret, concealed.