To take over the content of a message thread by
changing the subject of discourse to a topic outside the purview of the original subject and/orforum, while maintaining the subject line. A form of amusement for trolls. Threadjacking is distinguished from flaming, as flames are a quasi-personal attack on a poster or on a
poster's style of discourse, where threadjacking is deliberatly steering the discussion
offtopic.
Arm4war keeps starting
threads about how fighting style affects
gameplay, but artboy keeps threadjacking his posts with
rants about non-real world physics.