plesiochronous - technical definition

From the Greek plesio, meaning near, and chronos, meaning time, plesiochronous communications involves devices running at nominally the same rate. Plesiochronous networks comprise subnetworks and devices that are free-running, although at approximately the same rate and within defined parameters of tolerance for variation. Much as clocks and watches run at approximately the same rate, devices in a digital network are free-running, with some running at a slightly faster or slower pace.