ICations> 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)