1. A combination of two or more words, and/or their definitions, into one word.
EX. The Japanese are known for their use of Portmanteaus. Most Pokémon's names are portmanteau's, ex. Bulbasaur is a combination of "bulb", like the bulb of a plant, and "saur" meaning "lizard" in Latin, and, as a matter of fact, "Pokémon" is a well-known portmanteau of the words "Pocket" and "Monster" used, rather than the original name of the franchise because of copyright issues.
1. Theory. Recently, at the Pokémon Game Show in Japan, they unveiled a nifty little promo video about the history of the franchise starring Pikachu. At the end of said video, linked above, there is a static-filled shot of an HD Lucario standing abreast of a Blaziken in a street. Many game journalists have theorized what this could mean; could it be a new Stadium title, a new adventure game, or a new fighting game? With the release of information that Nintendo has copyrighted the terms "Pokkén Fighters" and " Pokkén Tournament" there can really only be one conclusion: there is going to be a Pokémon fighting game released on the Wii-U, and possible 3DS, in the style of Street Fighter or the similarly named Tekken. "Ken" or "兼" literally means "fist", so it can be assumed that Pokkén is a portmanteau of "Pokémon" and "Fist" or "Pokémon" and "Tekken" to represent the fact that this new game is going to be a Pokémon fighting game.
I'll keep you updated as news comes out about this barely rumored title.