rare

adjective

1. not widely known; especially valued for its uncommonness"a rare word"
2. recurring only at long intervals"a rare appearance"
3. not widely distributed"rare herbs"
4. having low density"rare gasses"
5. marked by an uncommon quality; especially superlative or extreme of its kind"what is so rare as a day in June"
6. (of meat) cooked a short time; still red inside"rare roast beef"