A Theoretical Virus is a fictional virus that is based on a real virus, but does not actually exist. They are used as a benchmark for viral preparedness. A good example of a theoretical virus is lyssa x, which is a relative of rabies. Web groups such as OZORT are geared toward preparing for worst case scenario viruses like these.
by Edward Stevens August 29, 2006
Noun (zee day): A term probably coined by Max Brooks which refers to the war between zombies and mankind. Derived from the word D-Day, which is a British term used to refer to a variable day on which a combat attack or operation is initiated. Z-Day is marked by a sudden attack on mankind by zombies, which will lead to a widespread zombie outbreak. There are a number of zombie survivalist groups worldwide (largely in the US, UK, and Canada), that are already planning what to do when this day comes.
Z-Day will catch mankind completely off guard, and the lack of preparation will lead to countless casualties.
by Edward Stevens August 26, 2006
"Lyssa" comes from a Greek word meaning "frenzy". It is a genus of viruses in the Rhabdovirida family that is characterised by it's ability to drive its victims into a mindless uncontrollable fits of fear and aggression (this includes humans). The most well known of member of this virus is Rabies. There are numerous members of this group, such as Mokola Virus, Duvenhage Virus, Irkut Virus, Khujand Virus, as well as the theorietical virus, Lyssa X.
by Edward Stevens August 28, 2006