You don't like wikipedia, how about Merriam-Webster? Canon: A sanctioned or accepted group or body of related works.
It's really difficult to argue with people when they don't even agree with the definition of the thing being debated. You guys are giving up your power as fans way too easily, happily accepting whatever sludge is shoved down your throats by whatever corporation happens to own the IP, narrative integrity be damned.
But fine, let's say canon is simply whatever we're being told is "official" by the current owner if the IP. In that case, cannon means NOTHING. That "canon" is simply a skin suit that can be bought and sold, and used by any hack creator with corporate backing as a way to disguise their mediocre, unspired, and/or insulting story as a genuine part of an already beloved universe with a built in fan base. It's nothing but a cheap commodity. The Ferengi would love that definition.