A vector quantity the scalar product of which with the cross sectional area vector is equal to the electric current. By magnitude it is the electric current divided by the cross sectional area.
Green Book, 2nd ed., p. 14 (https://dev.goldbook.iupac.org/files/pdf/green_book_2ed.pdf)
PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 971 (https://doi.org/10.1351/pac199668040957)