[ex.arch] n [LL exarchus, fr. LGk exarchos, fr. Gk, leader, fr. exarchein to begin, take the lead, fr. ex- + archein to rule, begin--more at arch-] (1588) 1: a Byzantine viceroy
2: an Eastern bishop ranking below a patriarch and above a metropolitan; specif: the head of an independent church -- ex.ar.chal adj -- ex.arch.ate n -- ex.ar.chy n
[2]exarch adj [exo- + -arch] (1891): formed or taking place from the periphery toward the center "~ xylem"