There are requests to "burninate" tags all over the place! What does this really mean; what happens to a burninated tag? How is it different than removing a tag or black-listing a tag? Would it be useful to include this definition in the Stack Overflow Glossary?
It's right there in the Meme question. It means just deleting a tag. With fire.
In all seriousness, here's what usually happens:
A tag, when it's burninated, is removed from all questions that carry this tag. This will just remove the tag from the system, but it can easily be re-created by users with the privilege to.
If a tag is really bad, and chances are it'll be recreated soon, then it can be blacklisted. Only few tags are blacklisted, but there are many good examples, such as homework on Stack Overflow, or the pc tag on Super User, which are both Meta tags and shouldn't exist.
To get a tag blacklisted, asking on the site's Meta is a good choice. This is nothing moderators can do—in fact moderators can't delete tags either—so it'll require community consensus and a developer to do that.