Definitions
from The American Heritage® Dictionary of the English Language, 4th Edition
 n. A polyhedron with 12 faces.
from Wiktionary, Creative Commons Attribution/ShareAlike License
 n. A polyhedron with twelve faces; the regular dodecahedron has regular pentagons as faces and is one of the Platonic solids.
from the GNU version of the Collaborative International Dictionary of English
 n. A solid having twelve faces.
from The Century Dictionary and Cyclopedia
 n. In geometry, a solid having twelve faces. Also duodecahedron.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
 n. any polyhedron having twelve plane faces
Etymologies
from The American Heritage® Dictionary of the English Language, 4th Edition
from Wiktionary, Creative Commons Attribution/ShareAlike License
Examples

A dodecahedron is any polyhedron with twelve faces, but usually a regular dodecahedron is meant: a Platonic solid composed of twelve regular pentagonal faces, with three meeting at each vertex.
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The hyperbolic dodecahedron is quite symmetric and has the same symmetry group as a regular dodecahedron.

To the ancient Greeks, the dodecahedron was a symbol of the Universe.
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The most likely explanation is that the dodecahedron was a cult object for the Pythagoreans (dodecahedra in stone and bronze have been found dating back to prehistoric times) and that it was because of these religious connections that Hippasus 'public work on the mathematical aspects of the solid was seen as impious (Burkert 1972a, 460).

Plato would certainly have found the structure of C60  an expanded dodecahedron, which is about as close to a sphere as you can get  to be an unusually beautiful body.

Place:  the temporal mood of the Oversoul, playing through that particular facet of the dodecahedron, which is Greece.

Maybe I was wrong to tell "dodecahedron" that the leftie troll spots were taken.

There was a dodecahedron floating in front of me, in every direction.

I had seen a set of models of the regular polyhedra in my High School trig class, and decided that a “12sided teetotum” must be the 12sdied thingy (a regular dodecahedron) I had seen in the set.

If one were to make every one of the Platonic solids with edges of the same length, the dodecahedron would be the largestwiki
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bilby commented on the word dodecahedron
Don't jump to Conclusions!
November 19, 2008
mollusque commented on the word dodecahedron
Yes, there are references to it at octopus, inner thesaurus and hippopotamonomatopoeia. But no one has made a Tollboth list yet . . .
November 19, 2008
obikitty commented on the word dodecahedron
Has anyone here read 'The Phantom Tollbooth'? The dodecahedron was one of my favorite characters when I read it as a kid.
November 19, 2008
milosrdenstvi commented on the word dodecahedron
It is often referred to by lower forms of life as a 'D12'.
August 16, 2008
chained_bear commented on the word dodecahedron
Constructing? Just saying this is teh alsome!
August 16, 2008
milosrdenstvi commented on the word dodecahedron
Constructing these is just totally awesome. I demonstrated it out of Euclid last year; basically you just mark off golden sections on a cube, raise equal lines perpendicularly, and connect the dots. I even made a model.
August 16, 2008