The merging of the words "Japan" and "Wannabe", Japannabe is a term used to describe (typically) white people who wish they were Japanese. These people usually have next to no knowledge of Japanese history, over-use the words "baka" and "kawaii", and even go so far as to claim they are Japanese.
Japannabe: omg u just hate me cuz u bumbed harosheemah lol
Genuine Asian: You do realise that the Tokyo firebombing was a worse offence, right? Please stop posing, gaijin.