American English

Definition of ballast noun from the Oxford Advanced American Dictionary

     

    ballast

     noun
    noun
    NAmE//ˈbæləst//
     
    [uncountable]
     
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  1. 1heavy material placed in a ship or hot-air balloon to make it heavier and keep it steady
  2. 2 a layer of stones that makes a strong base on which a road, railroad, etc. can be built
See the Oxford Advanced Learner's Dictionary entry: ballast