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)