Learner's definition of RARITY
1 [count] : a person or thing that is not common or usual: a person or thing that is not seen or does not happen often
In most sports, athletes over the age of 50 are rarities.
Snow is a rarity in this part of the world.
2 [count] : something that is valuable because there are few of its kind 3 [noncount] : the quality of being rare