A mathematical construct used in circuit analysis representing the current circulating around one specific closed loop. It is not always a physical current; when a wire is shared between two adjacent meshes, the actual physical current flowing through that branch is the algebraic sum of the two overlapping mesh currents.
Heard on the job
If mesh current one is 5 amps and mesh current two is 3 amps in the opposite direction, the shared resistor sees 2 amps.