Entry: dihedral (adj.)
In context: "The mattress, a Simmons Beauty Rest whose tag said it could not by law be removed, now formed the hypotenuse of a right dihedral triangle whose legs were myself and the bed's box spring."
Definition: Math. Of the nature of a dihedron
dihedron (n.): In the geometrical theory of groups, the portion of two superposed planes bounded by (or contained within) a regular polygon.
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SNOOT score: 1
Source: Oxford English Dictionary, Greg Egan