The Collaborative International Dictionary of English v.0.48:

Incumbent \In*cum"bent\, n.
   A person who is in present possession of a benefice or of any
   office.
   [1913 Webster]

         The incumbent lieth at the mercy of his patron.
                                                  --Swift.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Incumbent \In*cum"bent\, a. [L. incumbens, -entis, p. pr. of
   incumbere to lie down upon, press upon; pref. in- in, on +
   cumbere (in comp.); akin to cubare to lie down. See
   Incubate.]
   [1913 Webster]
   1. Lying; resting; reclining; recumbent; superimposed;
      superincumbent.
      [1913 Webster]

            Two incumbent figures, gracefully leaning upon it.
                                                  --Sir H.
                                                  Wotton.
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            To move the incumbent load they try.  --Addison.
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   2. Lying, resting, or imposed, as a duty or obligation;
      obligatory; always with on or upon.
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            All men, truly zealous, will perform those good
            works that are incumbent on all Christians. --Sprat.
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   3. (Bot.) Leaning or resting; -- said of anthers when lying
      on the inner side of the filament, or of cotyledons when
      the radicle lies against the back of one of them. --Gray.
      [1913 Webster]

   4. (Zool.) Bent downwards so that the ends touch, or rest on,
      something else; as, the incumbent toe of a bird.
      [1913 Webster]

The Devil's Dictionary (1881-1906):

INCUMBENT, n.  A person of the liveliest interest to the outcumbents.


Moby Thesaurus II by Grady Ward, 1.0:

89 Moby Thesaurus words for "incumbent":
   addressee, artist-in-residence, beetle, beetle-browed, beetling,
   behooving, benefice-holder, beneficiary, binding, bridging,
   burdensome, chargeable to, commanding, compulsory, cumbersome,
   cumbrous, demanding, denizen, dweller, habitant, hirer, holdover,
   homesteader, house detective, imbricate, impendent, impending,
   incumbent on, inhabitant, inhabiter, inmate, inpatient, ins,
   intern, jack-in-office, jutting, lame duck, lapping, leaseholder,
   lessee, live-in maid, locum tenens, lodger, lowering, lumpish,
   mandatory, massive, necessary, new broom, obligatory, occupant,
   occupier, office-bearer, officeholder, official, onerous,
   oppressive, overarched, overhanging, overhung, overlapping,
   overlying, paying guest, pending, prescribed, president-elect,
   projecting, public official, public servant, renter, required,
   residencer, resident, resident physician, residentiary, resider,
   roomer, shingled, sojourner, spanning, squatter, sublessee,
   subtenant, superincumbent, tenant, tenant at sufferance,
   tenant for life, underlessee, unwieldy