Heart-shaped.

ETYM Greek kardio-eides heart-shaped; kardia heart + eidos shape.
An epicycloid in which the rolling circle equals the fixed circle.
Heart-shaped curve traced out by a point on the circumference of a circle, resulting from the circle rolling around the edge of another circle of the same diameter.
The polar equation of the cardioid is of the form.
R = a(1 + cos q).