Refers to 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'.