genius UK /ˈd͡ʒiː.ni.əs/US /ˈd͡ʒin.jəs/noun 4adjective 1forms 4 noun4 •a person who is extremely smart or much better at something than almost everyone elseShe's a genius; she won a Nobel Prize at fifteen! •Extraordinary mental capacity. •Inspiration, a mental leap, an extraordinary creative process.to add a dash of cinnamon amid such umami was pure genius •The tutelary deity or spirit of a place or person.and the genius of the place: the growing enthusiasm for codified standards in the Army and Navy adjective1 •(informal) Ingenious, brilliant, very clever, or original.What a genius idea! formsgenii · geniuses · more genius · most genius