| 释义 |
WordReference Random House Learner's Dictionary of American English © 2024bal•last /ˈbæləst/USA pronunciation n. [uncountable]- Nauticalheavy material such as rock carried on ships to make them heavier and more controllable.
- Rail Transportgravel or broken stone placed under the ties of a railroad to keep the tracks steady.
WordReference Random House Unabridged Dictionary of American English © 2024bal•last (bal′əst),USA pronunciation n. - Nauticalany heavy material carried temporarily or permanently in a vessel to provide desired draft and stability.
- Aeronauticssomething heavy, as bags of sand, placed in the car of a balloon for control of altitude and, less often, of attitude, or placed in an aircraft to control the position of the center of gravity.
- anything that gives mental, moral, or political stability or steadiness:the ballast of a steady income.
- Rail Transportgravel, broken stone, slag, etc., placed between and under the ties of a railroad to give stability, provide drainage, and distribute loads.
- Electricity
- Also called ballast resistor. a device, often a resistor, that maintains the current in a circuit at a constant value by varying its resistance in order to counteract changes in voltage.
- a device that maintains the current through a fluorescent or mercury lamp at the desired constant value, sometimes also providing the necessary starting voltage and current.
- Nautical, Idioms, Naval Terms in ballast, carrying only ballast; carrying no cargo.
v.t. - Nautical, Naval Termsto furnish with ballast:to ballast a ship.
- to give steadiness to;
keep steady:parental responsibilities that ballast a person.
- Scandinavian; compare Old Danish, Old Swedish barlast, equivalent. to bar bare1 + last load; see last4
- Middle Low German, perh. ultimately
- 1520–30
Collins Concise English Dictionary © HarperCollins Publishers:: ballast /ˈbæləst/ n - any dense heavy material, such as lead or iron pigs, used to stabilize a vessel, esp one that is not carrying cargo
- crushed rock, broken stone, etc, used for the foundation of a road or railway track
- anything that provides stability or weight
- a device for maintaining the current in a circuit
vb (transitive)- to give stability or weight to
Etymology: 16th Century: probably from Low German; related to Old Danish, Old Swedish barlast, literally: bare load (without commercial value), from bar bare, mere + last load, burden |