Definitions
from The American Heritage® Dictionary of the English Language, 4th Edition
 adj. Having all sides or faces equal.
 n. A side exactly equal to others.
 n. A geometric figure having all sides equal.
from Wiktionary, Creative Commons Attribution/ShareAlike License
 adj. Referring to a polygon all of whose sides are of equal length. Not necessarily a regular polygon since the angles can still differ (a regular polygon would also be equiangular).
 n. An equilateral triangle
from the GNU version of the Collaborative International Dictionary of English
 adj. Having all the sides equal
 n. A side exactly corresponding, or equal, to others; also, a figure of equal sides.
from The Century Dictionary and Cyclopedia
 In geometry, having all the sides equal: as, an equilateral triangle.
 In zoology: Having the two sides equal: said of surfaces which can be divided into two parts of the same form by a longitudinal median line.
 Having all the sides equal.
 Having all the convolutions of the shell in one plane: said chiefly of foraminifers.
 n. A figure having all its sides equal.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
 n. a figure whose sides are all equal
 adj. having all sides or faces equal
Etymologies
Sorry, no etymologies found.
Examples

Ensure that the octagon is equilateral, meaning all sides on the ground have the same length.

a tiny mining company working claims in the remote "equilateral" cluster of asteroids far out in Jupiter's orbit.

It happened that the Lancashire Queen, the shore at Turner's Shipyard, and the Solano Wharf were the corners of a big equilateral triangle.

From the moment that grand trine appeared in the sky—an equilateral triangle like the great pyramids—it was our turn to clean house.

For example, if you enter 1, 3, 6, 10, 15, the server will tell you that is sequence A000217, the triangular numbers (these are the number of objects that can form an equilateral triangle like the standard arrangement of bowling pins.)
An Important AT&T Legacy Finds a New Home « Steve Wildstrom on Tech

Obtained by the rotation of 60 ° of two equilateral triangles superimposed and spaced in height, the form appears simple but at the same time full of spatial complexity.

How can anyone say that a scalene and an equilateral are really the same "kind"!

For example, three Woolworths sites around Birmingham form an exact equilateral triangle (Wolverhampton, Lichfield and Birmingham stores) and if the base of the triangle is extended, it forms a 173.8 mile line linking the Conway and Luton stores.

Richardson, Taylor and Tomlinson are scattered, forming a sort of equilateral triangle.

He noticed that the math books of his time gave two different methods for finding the area of an equilateral triangle  and that their answers did not agree.
Nancy Marie Brown: The Abacus And The Cross: When The Pope Was A Scientist:
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