Rare (adjective)

1. Infrequent or occurring in small numbers or in limited quantities.
2. Not commonly found or occurring, and often valuable or sought after.
3. Not well done or cooked, but still pink and juicy in the center, as with meat.

Origin:

Middle english rere, from old french rare, from latin rarus.

Examples:

1. The blue diamond is rare, and considered one of the most valuable gems in the world.
2. She found a rare book in the library, and felt lucky to be able to read it.
3. The steak was ordered rare, juicy and pink in the center, with a charred crust on the outside.
4. The bird watchers spotted a rare bird, and were excited to add it to their life list.
5. He loves rare coins, and collects them as a hobby, buying and selling them at auctions.