The bulk update request #10780 has been approved by @nonamethanks.
deprecate mouth
From the wiki page: "For images with an overwhelming focus on mouths (ex. post #993583, post #668688) or mouths in unusual places (ex. post #931404, post #986045)."
Not only are those two basically unrelated definitions, most of the posts on the first few pages (ex. post #5330041, post #5197623, post #5107318) don't fit them at all.
I suggest making a new tag, mouth focus, for the former definition, and then some other tag for which i can't come up with a sufficiently descriptive yet succinct name for the second definition. maybe we could also populate and clean up big mouth while we're at it.