dam

In a sentence

• Le castor construit un barrage dans la rivière.

  The beaver builds a dam in the river.

  Here, "barrage" refers specifically to a structure blocking the flow of water in a river, which is the literal meaning of 'dam' in French.

• La construction du barrage hydroélectrique prendra plusieurs années.

  The construction of the hydroelectric dam will take several years.

  In this sentence, "barrage" denotes a man-made structure used for generating electricity by harnessing water flow.

• Nous avons visité un barrage militaire qui défendait la frontière.

  We visited a military dam that defended the border.

  While less common, 'barrage' can metaphorically refer to a blockade or defensive structure. Here, it has a military context of obstructing or controlling movement.