In geometry, a tetrahedrally diminished[a] dodecahedron (also tetrahedrally stellated icosahedron or propello tetrahedron[1]) is a topologically self-dual polyhedron made of 16 vertices, 30 edges, and 16 faces (4 equilateral triangles and 12 identical quadrilaterals).
[2] A canonical form exists with two edge lengths at 0.849 : 1.057, assuming that the radius of the midsphere is 1.
Topologically, the triangles are always equilateral, while the quadrilaterals are irregular, although the two adjacent edges that meet at the vertices of a tetrahedron are equal.
[3] As a diminished regular dodecahedron, with 4 vertices removed, the quadrilaterals faces are trapezoids.
[4] In Conway polyhedron notation, it can be represented as pT, applying George W. Hart's propeller operator to a regular tetrahedron.