What does "equilateral" mean?

Equilateral: Having all the sides equal; as, an equilateral triangle; an equilateral polygon. Equilateral hyperbola (Geom.), one whose axes are equal. -- Equilateral shell (Zoöl.), 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.