The big tag has almost 2000 posts associated to it, but is completely contextless. It's far too ambiguous for our tagging purposes.

What should we do with it?

I'm personally leaning toward alias -> invalid_tag, but maybe someone actually gives enough of a shit to take on a retagging project to identify exactly what is "big" in the image?

I agree with this, and as an aside, I looked up "small", just for grins. We have 60 instances of this tag and like "big" it's being used for different, entirely unrelated things.

At least there's no "medium" tag. However, there's "huge", "large" and "tiny" -- all completely contextless, like "big".

Well it's usually describing the characters themselves (but not macro big), and it's ambiguous because we have big_* for body parts, so this is for characters

Aside, I'd be more in favor of aliasing big (and large, tiny, small) to two better terms, rather than nuking

Isn't that what we have size_difference for?

And we ought to generalize it instead of saying that it's "generally applied only to pictures depicting sex".