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

genius

noun

ˈdʒiːniəs

ˈdʒiːniəs

plural geniuses

1 [uncountable] unusually great intelligence, skill or artistic abilitythe genius of Shakespearea statesman of geniusHer idea was a stroke of genius.2 [countable] a person who is unusually intelligent or artistic, or who has a very high level of skill, especially in one areaa mathematical/comic, etc. geniusHe's a genius at organizing people.You don't have to be a genius to see that they are in love!3 [singular] genius for something/for doing something a special skill or abilityHe had a genius for making people feel at home.

Idioms

somebody's good/evil genius

(especially British English) a person or spirit who is thought to have a good/bad influence over you