# What is the definition of current efficiency?

What is the exact definition of current efficiency of an electrolytic cell? I've looked online and there is no suitable answer to it.

I thought current efficiency would be the amount of electrons that actually participate in a desired reaction. For example, if we are electrolyzing a an aqueous solution of $\ce{FeCl3}$ and we have a $\pu{10A}$ current running for, say, $\pu{100 s}$, at $60\%$ current efficiency, two possible products are $\ce{H2}$ gas and reduced $\ce{Fe}$ metal. Current efficiency of $60\%$ means that half of the electrons that pass through this circuit would reduce the $\ce{Fe}$ instead of reducing $\ce{H2}$.

However, there is another way to think about it, in that it means 60% of the theoretical mass yield of $\ce{Fe}$ comes out of the reaction instead of my original definition, which is different because the reduction of iron (III) requires 3 electrons rather than only 2 electrons for the reduction of $\ce{H2O}$/$\ce{H+}$ ions. So what is the actual definition?