\E`qui*lat"er*al\, a. [L. aequilateralis; aequus
equal + latus, lateris, side: cf. F. ['e]quilat['e]ral.]
Having all the sides equal; as, an equilateral triangle; an
equilateral polygon.
{Equilateral hyperbola} (Geom.), one whose axes are equal.
{Equilateral shell} (Zo["o]l.), one in which a transverse
   line drawn through the apex of the umbo bisects the valve,
   or divides it into two equal and symmetrical parts.
{Mutually equilateral}, applied to two figures, when every
   side of the one has its equal among the sides of the
   other.

\E`qui*lat"er*al\, n.
A side exactly corresponding, or equal, to others; also, a
figure of equal sides.