1. of a triangle: having two sides of equal length
Usage: geometry; standard mathematical term

Examples

• An isosceles triangle has two equal sides and two equal angles.
• The architect designed the roof in the shape of an isosceles triangle.
• In an isosceles triangle, the base angles are congruent.
• She drew an isosceles triangle with sides of 5, 5, and 8 centimeters.
• The isosceles trapezoid has two parallel sides and two equal non-parallel sides.