1. A mathematical operation, symbolized by "x", that for integers is equivalent to adding a number to itself a particular number of times: "Three times (x) three equals nine (3 x 3= 9)."
2. A mathematical operation equivalent to multiplication extended to expressions; such as, functions or matrices that are not numbers.
3. A marked increase in number or amount: "There was a multiplication of claims made by people who lost their homes as a result of the hurricane."
4. The act or process of reproduction in animals, plants, people, etc.

1. The ratio of the average amount of current density at a given opening to the average current density at the cathode surface.
2. A ratio of the average current density at any specified opening through which the electron stream passes to the average current density at the cathode surface.