necrothreadia 

The term used when, on a forum, a user revives a thread that is long dead.

Necrothreadia is when the date is 10/04/05 and someone posts on a thread that is dated 24/12/99.

necrothreadia by Noopectro April 10, 2005

necrothread 

Negatively: an old, decaying thread that refuses to die.

Positively: a threaded conversation that had retained its usefulness so long that new comments are still being added years later.

Example relates to both definitions.

Example of a necrothread: "Where's the best place to meet people in (insert city here)?"

necrothread by Amber Spyglass January 4, 2009

necrothreadiac 

The term given to someone who constantly practices necrothreadia.

Billy is said to be a necrothreadiac when he posts on several topics from the year 1999, when the actual year is 2005.

necrothreadiac by Noopectro April 10, 2005