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)