1. Genetics The offspring of genetically dissimilar parents or stock, especially the offspring produced by breeding plants or animals of different varieties, species, or races.
a. Something of mixed origin or composition, such as a word whose elements are derived from different languages.
b. Something having two kinds of components that produce the same or similar results, such as a vehicle powered by both an electric motor and an internal combustion engine as sources of power for the drive train.
I don't care what WoW has told you.
That's a real hybrid.
If you want to call a class with 3-4 distinct roles a hybrid when they can only perform one role (competitively) at a time, feel free.