Nearly synchronised, a term describing a communication system where transmitted signals have the same nominal digital rate but are synchronised on different clocks. AccORding to ITU-Tstandards, cORresponding signals are plesiochronous if their significant instants occur at nominally the same rate, with any variation in rate being constrained within specified limits. [Pronunciation? /ples' ee-oh-kroh' nus/?] (1995-03-02)