Definitions

1. adjective

extremely rare or uncommon

“This species is considered the rarest in the world, with only a few individuals remaining.”

2. noun

the rarest of something

“The rarest is the limited edition of the new video game that only a few people were able to purchase.”

3. adverb

to a very great extent or degree

“He is the rarest of the artists to have received such a prestigious award at such a young age.”