Meltdown

[melt-doun] /ˈmɛltˌdaʊn/

noun
1.
the melting of a significant portion of a nuclear-reactor core due to inadequate cooling of the fuel elements, a condition that could lead to the escape of radiation.
2.
a quickly developing breakdown or collapse: a bond-market meltdown;
the meltdown of a marriage.
3.
Informal. a sudden loss of control over one’s feelings or behavior:
My toddler had a meltdown when I tried to leave the house.
/ˈmɛltˌdaʊn/
noun
1.
(in a nuclear reactor) the melting of the fuel rods as a result of a defect in the cooling system, with the possible escape of radiation into the environment
2.
(informal) a sudden disastrous failure with potential for widespread harm, as a stock-exchange crash
3.
(informal) the process or state of irreversible breakdown or decline: the community is slowly going into meltdown
n.

by 1937 in the ice-cream industry; by 1956 in reference to a nuclear reactor, from verbal phrase, from melt (v.) + down (adv.). Metaphoric extension since 1979.
meltdown
(mělt’doun’)
Severe overheating of a nuclear reactor core, resulting in melting of the core and escape of radiation.

The most serious accident that can occur at a nuclear reactor. In a meltdown, the radioactive material in the reactor becomes very hot, melting some or all of the fuel in the reactor. A meltdown may or may not be followed by the release of radioactive material to the environment. A partial meltdown, with very little external radiation, occurred at Three Mile Island in 1979; a complete meltdown happened at Chernobyl in 1986.

noun phrase

Something very long and tedious told or explained exhaustively: I’ve been listening to all this here Megillah/Let’s not have the megillah/a whole megilla (song and dance)

[1909+; fr Yiddish fr Hebrew, ”scroll, volume,” esp the Book of Esther read aloud in its entirety at Purim celebrations]

network meltdown