'But "glory" doesn't mean "a nice knock-down argument,"' Alice objected.
'When I use a word,' Humpty Dumpty said in rather a scornful tone, 'it means just what I choose it to mean — neither more nor less.'
'The question is,' said Alice, 'whether you can make words mean so many different things.'
'The question is,' said Humpty Dumpty, 'which is to be master — that's all.'
(Lewis Carroll, Through the Looking-Glass)
Linguists agree with Lewis Carroll's Alice: You can't make words mean "just what you choose them to mean" because word meanings are the product of collective behavior. A given word could mean absolutely anything — "glory" could indeed mean "a nice knock-down argument" — but do mean only what people use them to mean. If, tomorrow, everyone started using "glory" to mean "a nice knock-down argument," that would become one of the word's meanings.
The internet hasn't changed this basic fact about language. But because it has changed the speed with which any one person can share an idea and persuade others to adopt it, it has moved us closer to the point where, in principle, I could invent a new word or decide on a new meaning for an existing word and transform my desire into reality.