noun

a barrier constructed to hold back water and raise its level, forming a reservoir used to generate electricity or as a water supply.

the dam burst after torrential rain

barrage,barrier,wall,embankment,levee,barricade,obstruction,hindrance,blockage

verb

build a dam across (a river or lake).

the river was dammed to form Lake Powell

block (up),obstruct,choke,clog (up),bung up,close,occlude