I. as at equiangular + adjective
Etymology: Late Latin aequilateralis, from Latin aequi- equi- + lateralis lateral — more at lateral
1.
a. : having all the sides equal
an equilateral triangle
an equilateral polygon
b. of a polyhedron : having all the faces equal
2. : bilaterally symmetrical ; specifically of a bivalve shell : divisible into two equal and symmetrical parts by a transverse line drawn through the apex of the umbo
II. noun
( -s )
1. : a side exactly corresponding or equal to others
2. : a figure of equal sides