Oxford Advanced American Dictionary

Definition of lion noun from the Oxford Advanced Learner's Dictionary

lion

noun
lion pronunciation English ˈlaɪən lion pronunciation American ˈlaɪən
 
a large powerful animal of the cat family, that hunts in groups and lives in parts of Africa and southern Asia. Lions have yellowish-brown fur and the male has a mane (= long thick hair round its neck).
compare lioness see also mountain lion
Idioms

the lion's den

a difficult situation in which you have to face a person or people who are unfriendly or aggressive towards you

the lion's share (of something)

(British English) the largest or best part of something when it is divided
 more at beard the lion in his den at beard verb see also the British Lions