A person who comments on a thread dedicated to a topic they pretend to abhor but secretly find fascinating, if for no other reason than they are compelled to act out a deep-seated impulse to be a total opinionated douche bag. This condition is often coupled with bitchitus and in some people can lead to chronic dickiness.
If one encounters a threadbear squatting on a site, it is best to let it shit then move on without interruption.
When the hairline of a person is so low that their forehead becomes reclassified a "threehead". This also suggests that their forehead is only about three finger widths high.
Describing a state where a person's brain can't process information quickly. This is not to say that they are outright stupid, just slower than average. Origin comes from field of computing where threads represent units of processing in a system capable of concurrent processing.
How single-threaded was Brian in that meeting today? He was not keeping up at all.
Totally. Anthony was much better - across everything that was going on. He's one multi-threaded mo-fo.