What is Rare ?
Rare is (adj) 1. unusual, not common It’s very rare to meet a foreigner who speaks perfect Chinese. Experienced sales staff are rare these days. The woodland is the habitat of a rare species of frog. 2. (of meat) which is very lightly cooked How would you like your steak? Rare, please! (NOTE: rarer rarest)
source: Easier English, Student Dictionary Upper Intermediate Level