ATions> 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)