The term 'HORSE TRACK SHAPE' is referring to the shape of a horse racing track, which is an OVAL. The word 'OVAL' is a 4-letter word that is used to describe the shape of a horse racing track. An OVAL is a closed curve in a plane where the sum of the distances from any point on the curve to two fixed points is constant. It is a symmetrical shape with two long curved sides and two shorter straight sides.