Icosahedron
Definition of icosahedron:
part of speech: noun
(
geom.)
A
solid
having
twenty
equal
sides
or
faces.
Usage examples for icosahedron:

If
you
cut
out
a
piece
of
cardboard
of
the
form
shown
in
the
smaller
diagram,
and
cut
half
through
along
the
dotted
lines,
it
will
fold
up
and
form
a
perfect
icosahedron
"Amusements in Mathematics", Henry Ernest Dudeney.

In
particular
Plato
tells
us
that
they
asserted
that
the
four
elements
of
the
real
world
were
the
tetrahedron,
octahedron,
icosahedron
and
cube,
and
Plutarch
ascribes
this
doctrine
to
Pythagoras
himself.
"The Teaching of Geometry", David Eugene Smith.

The
five
regular
solids,
in
appropriate
order
Octahedron,
Icosahedron
Dodecahedron,
Tetrahedron,
Cube.
"Pioneers of Science", Oliver Lodge.

Within
the
Earth's
orbit
inscribe
an
icosahedron
the
sphere
inscribed
in
it
will
be
Venus's
orbit.
"The Astronomy of Milton's 'Paradise Lost'", Thomas Orchard.