English▸ noun
1 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
[in names] the Hoover Dam.
▪ a barrier of branches in a stream, constructed by a beaver to provide a deep pool and a lodge.
2 (also dental dam) a rubber sheet used to keep saliva from the teeth during dental operations, or as a prophylactic device during cunnilingus and anilingus.
▸ verb
(dams, damming, dammed)
[with object] build a dam across (a river or lake): the river was dammed to form Lake Powell.
▪ hold back or obstruct (something):
the closed lock gates dammed up the canal
figurative discussion was in full flow and refused to be dammed.
– ORIGIN Middle English : from Middle Low German or Middle Dutch; related to Dutch dam and German Damm, also to Old English fordemman ‘close up’.