Cosplay and Corsets

So what exactly IS cosplay? I'm sure we all have our own version of description here. But here is what the dictionary says: 

According to Google Dictionary, this is the definition of Cosplay: the practice of dressing up as a character from a movie, book, or video game, especially one from the Japanese genres of manga and anime.

I mean really? Japanese? Cosplay to me is literally any form of dress up. From Disney to Steampunk and everything in between! Googles definition is far too restrictive in its description of what cosplay is.