it's forum slang, means resurrected, but in a negative way, basically means an old topic that was dead was posted in again and usually the content wasn't worth resurrecting. It's a forum etiquette thing, but each forum has its own policy of necroes. and necro itself isn't a word i do believe, but necrophiliac has to do with death and thus i think that's partly where the term necro is derived. but yeah, most sites have a several week rule with posts, such that any post that hasn't been posted in for a few weeks is dead and therefore shouldn't be posted in again, and the more time passes, the more offensive it is to post in the topic. Now on my forum I run it such that I don't cre as long as the content of the necro post was worth bringing the post "back from the dead"