Webster's Revised Unabridged Dictionary · 1913

Equilateral

Equilateral , adjective

[Latin aequilateralis; aequus equal + latus, lateris, side: compare French équilatéral.]

Having all the sides equal; as, an equilateral triangle; an equilateral polygon.
Collocations (3)
Equilateral hyperbola (Geometry) , one whose axes are equal.
Equilateral shell (Zoology) , 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.

Equilateral , noun

A side exactly corresponding, or equal, to others; also, a figure of equal sides.