Nikkei indexPronunciation: /ˈnɪkeɪ/Definition of Nikkei index a figure indicating the relative price of representative shares on the Tokyo Stock Exchange. Also called Nikkei average. Origin: 1970s: Nikkei, abbreviation of Ni(hon) Kei(zai Shimbun) 'Japanese Economic Journal'Nikkei index in other Oxford dictionaries Definition of Nikkei index in the US English dictionary