If you have a link to the video or a screenshot of where you saw this title, I can help you identify its specific origin or determine if it is a safe file to open.
The term appears to be a composite of niche internet subcultures. While "Grandmaster Troll" is a common label for high-level online agitators—often seen in communities like Kongai Wiki or used to describe competitive chess players like Magnus Carlsen—the specific ".mp4" filename format typically points to one of the following: GrandMaster Troll Hijacked Video.mp4
A "hijacked video" is often a bait-and-switch meme where a normal video abruptly cuts to unexpected footage (e.g., loud noises, "screamer" jump scares, or Rickrolling). If you have a link to the video