Longman Dictionary of Contemporary English homepage

Date: 1500-1600
Origin: Probably from Low German

ballast

noun
     
Related topics: Air, Roads, Water
bal‧last [uncountable]
1TTW heavy material that is carried by a ship to make it more steady in the water
2TTA material such as sand that is carried in a balloon so that it can be thrown out to make it rise
3TTR a layer of broken stones that a road or railway line is built on

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