A meme which revolves around multi-line text (typically four-word phrases) arranged in a manner where it is unclear whether the words should be read in row-major or column-major order.
The name originates from a promotional poster for The Walking Dead which depicts a double-door with the words 'don't open' 'dead inside' grouped into columns written on the two door panels, such that it reads horizontally as 'don't dead' 'open inside'.
The meme saw renewed interest with the more recent Sasa Lele example, as featured in post #4626342.
