the amount of electric current passing through a cross-sectional area (perpendicular to the direction of current) of a conductor in a given unit of time: commonly expressed in amperes per square centimeter or amperes per square inch
See current density in American Heritage Dictionary 4
current density
noun
Symbol j, JElectricity A vector quantity whose magnitude is the ratio of the magnitude of current flowing in a conductor to the cross-sectional area perpendicular to the current flow and whose direction points in the direction of the current.
Physics The number of subatomic particles per unit time crossing a unit area in a designated plane perpendicular to the direction of movement of the particles.