adj. & n.
adj. 1 (foll. by on, upon) resting as a duty (it is incumbent on you to warn them). 2 (often foll. by on) lying, pressing.
n. the holder of an office or post, esp. an ecclesiastical benefice.
[ ME f. AL incumbens pres. part. of L incumbere lie upon (as IN-(2), cubare lie) ]