a sample taken from a larger group that represents the typical members or elements of the group;
e.g. They are looking to survey a cross section of the neighborhood's population.
(noun)
a straight cut made through something at right angles to one of its axes, the surface exposed by such a cut, a "slice" taken by two such cuts, or a representation (such as a diagram or model) of this surface;
e.g. He took a cross section of the fruit and looked inside. The diagram showed a cross section of the human heart.