Find the word definition

Wiktionary
res nullius

phr. (context legal English) Something that has no owner, and not subject to jurisdiction of any state, susceptible to national appropriation.

Wikipedia
Res nullius

Res nullius (lit: nobody's property) is a Latin term derived from Roman law whereby res (an object in the legal sense, anything that can be owned, even a slave, but not a subject in law such as a citizen) is not yet the object of rights of any specific subject. Such items are considered ownerless property and are usually free to be owned.

Examples of res nullius in the socio-economic sphere are wild animals or abandoned property. Finding can also be a means of occupation (i.e. vesting ownership), since a thing completely lost or abandoned is res nullius, and therefore belonged to the first taker. Specific legislation may be made, e.g. for beachcombing.