Unobtainable (adjective)

1. Not able to be gotten, acquired, or attained.
2. Not possible to obtain or attain.
3. Not accessible or attainable.

Origin:

From the latin word 'inobtinere' which means 'not to get or attain'.

Examples:

1. The rare species of plant was considered unobtainable by most botanists.
2. The artifact was said to be unobtainable, but the adventurer managed to find it.
3. The information was deemed unobtainable, but the detective was able to uncover it.
4. The goal was thought to be unobtainable, but the team was able to achieve it.
5. The treasure was considered unobtainable, but the pirate managed to find it.