It serves everyone to have relatively stable meanings for words and phrases. "Relatively" because of course there is natural drift over time. But if today I write "big data" and it means "millions of rows in Excel" to Bob but "hundreds or thousands of terrabytes" to Jane, it's effectively useless to use in communication.

Put another way, that Bob thinks he's dealing with "big data" doesn't mean he is in fact.

In four lines you manage to be arrogant, insulting, patronizing, and intellectually sloppy (“by definition”?) I'm disappointed. I'd like to invite you to produce a higher level of discourse.

...you can't be serious. This is an incredibly over the top reaction to a very mild reply. Not to mention that telling me you're disappointed in me and inviting me to "produce a higher level of discourse" is far more arrogant and patronising than anything in my original statement.

But anyway, this is very obviously off-topic. I don't think it serves the wider community to continue this conversation so I'll leave it here.

Well, I'm certainly guilty of the same offense!