A nerdy term relating to discussions of hypothetical situations in a computer game. Originates from the Starcraft community and was later adopted en masse by the similarly geeky Warcrafters.
Nerd 1: if ur a X n u Y every Z u fight u omgwtfpwn them every time, lolz!!!111eleven
Nerd 2: Well considering Z's don't exist yet, that's theorycraft
Nerd 1: I'm sick of theorycrafters, don't they have anything better to do?
Nerd 2: Not really