- meltdown, nuclear meltdown - severe overheating of the core of a nuclear reactor resulting in the core melting and radiation escaping
--1 is a kind of overheating
- meltdown - a disaster comparable to a nuclear meltdown; "there is little likelihood of a meltdown comparable to the American banking collapse in March 1933"
--2 is a kind of calamity, catastrophe, disaster, tragedy, cataclysm