NOUN (1)

1. a figure whose sides are all equal;


ADJECTIVE (1)

1. having all sides or faces equal;

The Collaborative International Dictionary of English v.0.48:

Equilateral \E`qui*lat"er*al\, n.
   A side exactly corresponding, or equal, to others; also, a
   figure of equal sides.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Equilateral \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.
   [1913 Webster]

   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.
      [1913 Webster]

WordNet (r) 3.0 (2006):

equilateral
    adj 1: having all sides or faces equal
    n 1: a figure whose sides are all equal

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "equilateral":
   balanced, coequal, coordinate, equal, equiangular, equidimensional,
   equiproportional, equisided, equisized, equispaced, eurythmic,
   even, finished, harmonious, isometric, proportioned, regular,
   symmetric, uniform, well-balanced, well-set, well-set-up