in·cum·bent 
(ĭn-kŭmbənt)
(ĭn-kŭmbənt)adj.
1. Imposed as an obligation or duty; obligatory: felt it was incumbent on us all to help.
2. Lying, leaning, or resting on something else: incumbent rock strata.
3. Currently holding a specified office: the incumbent mayor.
n.
A person who holds an office or ecclesiastical benefice: The incumbent was reelected to another term.
[Middle English, holder of an office, from Medieval Latin incumbēns, incumbent-, from Latin, present participle of incumbere, to lean upon, apply oneself to : in-, on; see IN-2 + -cumbere, to recline.]
in·cumbent·ly adv.