E`qui*lat"er*al (?), a. [L. aequilateralis; aequus equal + latus, lateris, side: cf. F. équilatéral.] 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.

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