n.在职官员；adj.义不容辞，有责任的,
Merriam-Webster Online Dictionary
incumbent (noun)1.
the holder of an office or - ecclesiastical benefice
2.
one that occupies a particular position or place
1.
as a duty - imposed obligatory incumbent on us to take action
2.
having the status of an incumbent - (see incumbent) the team's incumbent third baseman , especially occupying a specified office - the incumbent mayor
3.
lying or resting on something else
4.
bent over so as to rest on or touch an underlying surface
Merriam-Webster Online Thesaurus
incumbent (adjective)forcing one's compliance or participation by or as if by law
SYNONYMS:
compulsory, forced, imperative, incumbent, involuntary, necessary, nonelective, obligatory, peremptory, requiredRELATED WORDS:
all-important, essential, indispensable, needed, requisite; insistent, persistent, pressing, urgent; demanded, enforced; coerciveNEAR ANTONYMS:
chosen, discretionary; dispensable, unnecessary, unneeded, unwanted; inconsequential, insignificant, nonessential, unimportant