superincumbent (adj) – lying or resting on something else; exerting pressure on something
BREAKDOWN: SUPER- (over or above) + IN- (on) + CUMB- (to lie) + -ENT (being or inclined to)
This word is built on the root CUMB-, which means to lie down.
Common CUMB- words include succumb.
More esoteric CUMB- words include accumbent and procumbent.