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1. Lit. [for something frozen] to melt. The glacier melted down little by little. When the ice on the streets melted down, it was safe to drive again.
2. Fig. [for a nuclear reactor] to become hot enough to melt through its container. The whole system was on the verge of melting down.
melt something down
to cause something frozen to melt; to cause something solid to melt. The rays of the sun melted the candle down to a puddle of wax. The heat melted down the ice.
1. To melt from a solid into a liquid: As ice cubes melt down, the water level in the glass remains constant.
2. To cause something to melt from a solid into a liquid: The sun melted the snowman down into a puddle. I melted down the ice on the window with a hair dryer.
3. To overheat severely and melt, resulting in the escape of radiation from a nuclear reactor core: The nuclear reactor melted down, and thousands of people had to evacuate the area.
4. Slang To have an emotional breakdown: I was dealing with a lot of stress, and I melted down on the subway when it stopped between stations.