Definition of isosceles in English:
 isosceles
adjective ʌɪˈsɒsɪliːzaɪˈsɑsəˌliz
(of a triangle) having two sides of equal length.
 Example sentencesExamples
-  The base angles of an isosceles triangle are equal.
 -  This is the ‘alternate’ solution to constructing the isosceles triangle with the base of the square as one side, using only a straightedge.
 -  The base of the wedge is an isosceles right triangle in a vertical plane.
 -  First construct an isosceles triangle whose base angles are double the vertex angle.
 -  Mathematicians sometimes say that A is an arbitrary isosceles triangle, but all they mean is that A could be any such triangle.
 
Origin
  
Mid 16th century: via late Latin from Greek isoskelēs, from isos 'equal' + skelos 'leg'.
   Definition of isosceles in US English:
 isosceles
adjectiveīˈsäsəˌlēzaɪˈsɑsəˌliz
(of a triangle) having two sides of equal length.
 Example sentencesExamples
-  The base angles of an isosceles triangle are equal.
 -  Mathematicians sometimes say that A is an arbitrary isosceles triangle, but all they mean is that A could be any such triangle.
 -  This is the ‘alternate’ solution to constructing the isosceles triangle with the base of the square as one side, using only a straightedge.
 -  First construct an isosceles triangle whose base angles are double the vertex angle.
 -  The base of the wedge is an isosceles right triangle in a vertical plane.
 
Origin
  
Mid 16th century: via late Latin from Greek isoskelēs, from isos ‘equal’ + skelos ‘leg’.