Wow, someone's getting a little worked up over semantics.
That's a very obscure definition of theory and is not how the word is generally used, the first three are the ones that are generally used.
A set of statements or principles devised to explain a group of facts or phenomena, especially one that has been repeatedly tested or is widely accepted and can be used to make predictions about natural phenomena.
The branch of a science or art consisting of its explanatory statements, accepted principles, and methods of analysis, as opposed to practice: a fine musician who had never studied theory.
A set of theorems that constitute a systematic view of a branch of mathematics.
And actually, if you want to really be technical, in science very very rarely is anything said to be disproven or proven until there is an overwhelming amount of evidence. It's either supported or not supported.