ballast
noun/ˈbæləst/
/ˈbæləst/
[uncountable]- heavy material placed in a ship or hot-air balloon to make it heavier and keep it steadyTopics Transport by waterc2
- a layer of stones that makes a strong base on which a road, railway, etc. can be built
Word Originmid 16th cent.: probably of Low German or Scandinavian origin.
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ballast