What is your definition of a Troll?

I am interested, I have been on the internets for a long time, and during that time have seen the meaning of the word change. I myself have been banned from many a site for being labeled a Troll, but the definition that is used today seems to be;

Troll - Someone who disagrees with me.

The world seems to have gone PC mad.

Could everyone please use the reverse of what they would usually use for any upvote/downvote on this thread. That would be great :)