to remove unwanted things from the bottom of a river, lake, etc. using a boat or special device

They have to dredge the canal regularly to keep it open. 为了保持运河的畅通他们必须定期进行清淤作业。

to search an area of water by dredging

The police are dredging the lake for his body. 警方在湖中打捞他的尸体。

They dredged up (= brought to the surface) all sorts of rubbish from the bottom of the river. 他们从河底捞出了各种各样的垃圾。

to drop flour, sugar, etc. over food

Lightly dredge the cake with icing sugar. 在蛋糕上薄薄地撒一层糖霜。

dredge something up 翻（旧账），揭（伤疤），重提（不快往事）