B1 not common; very unusual稀少的；罕见的；不常发生的
They mainly deal in rare books.
The coast here abounds with rare plants.
Talent like hers is rare in someone so young.
The word itself is so rare as to be almost obsolete.
He has a collection of rare insect specimens.
C1 (of meat) not cooked for very long and still red（肉）煮得半熟的，煎得嫩的
used to describe the air at the top of a mountain, which contains less oxygen, making it harder to breathe（山顶空气）稀薄的