Japanese emigrants and their descendants living outside (and sometimes inside) Japan. A broader term (since it includes Japanese Brazilians, Japanese Canadians, etc.), "Nikkei" it has come to be used as an alternative to "Japanese American" by some. As a newer term, how exactly one is to use it—and who is or is not Nikkei—is still being worked out.
A handful of Japanese American organizations use the term "Nikkei" instead of "Japanese American"; see for instance the Oregon Nikkei Legacy Center (http://www.oregonnikkei.org/) or the San Jose Nikkei Matsuri (http://www.nikkeimatsuri.org/).
"Nikkei" is also the name of a popular index for the Tokyo Stock Exchange, akin to the Dow Jones Industrial Average for the New York Stock Exchange.
For More Information
Discover Nikkei. http://www.discovernikkei.org/en/. [A project of the Japanese American National Museum, brings together resources from Nikkei communities around the world.]
Hirabayashi, Lane Ryo, Akemi Kikumura-Yano, and James A. Hirabayashi, eds. New Worlds, New Lives: Globalization and People of Japanese Descent in the Americas and from Latin American in Japan. Stanford: Stanford University Press, 2002.
Kikumura-Yano, Akemi, ed. Encyclopedia of Japanese Descendants in the Americas: An Illustrated History of the Nikkei. Walnut Creek, CA: AltaMira Press, 2002.