The 'Fourth Hole' meme is a recurring internet trope that centers on the shock, confusion, or feigned ignorance regarding a hypothetical or biological 'fourth hole.' It often thrives on 'cursed' knowledge or urban legends, where one person mentions it and others react with horror or disbelief. Typically used in reaction image formats or 'Search History' memes, it plays on the viewer's curiosity and the subsequent regret of finding out the answer. It has become a staple in dark humor circles and social media platforms like TikTok and Twitter to bait engagement through mystery and the fear of the unknown.