dodecahedron UK /ˌdəʊ.dɛk.əˈhiː.dɹən/US /ˌdoʊ.dɛk.əˈhiː.dɹən/ noun1 •A polyhedron with twelve faces; the regular dodecahedron has regular pentagons as faces and is one of the Platonic solids.Dodecahedron, (Gr.) in Geometry, is a solid Figure of 12 Sides or Faces that are regular Pentagons, it is one of the Platonick or Regular Bodies. — 1707 formsdodecahedra · dodecahedrons