exarch
Concise Oxford English Dictionary © 2008 Oxford University Press:
exarch /ˈɛksɑːk/
▶noun
- 1 (in the Orthodox Church) a bishop lower in rank than a patriarch and having jurisdiction wider than the metropolitan of a diocese.
- 2 historical a governor of a distant province under the Byzantine emperors.
– origin C16: via eccles. L. from Gk exarkhos, from ex- ‘out of’ + arkhos ‘ruler’.
'exarch' also found in these Oxford entries:

