meltdown

noun

Etymology: From melt (verb) + down (adverb), a deverbal from melt down (verb).

1. An act or process of melting.
2. An act or process of melting.

   “Thus began by far the gravest crisis in the troubled, 32-year history of commercial atomic power. A catastrophe had occurred over the weekend at the Chernobyl plant, 80 miles north of Kiev, where a reactor meltdown and explosion caused untold death and suffering and raised the prospect of long-term health and environmental damage on a far greater scale than anything yet unleashed by peaceful nuclear use.”

3. A mass of melted material.
4. Chiefly preceded by a descriptive word: uncontrolled disorder which often has disastrous consequences; (countable) a situation involving this; a crisis.

   “Channel 4 switchboards went into meltdown this week when viewers called to complain about a Brass Eye programme on child sex.”

   “Computer engineers were at a loss last night to explain why the Government had been hit by arguably the worst electronic meltdown in the history of Whitehall.”

5. Chiefly preceded by a descriptive word: uncontrolled disorder which often has disastrous consequences; (countable) a situation involving this; a crisis.
6. (Sudden) loss of control over one's behaviour, emotions, etc.; (countable) an instance of this.
7. (Sudden) loss of control over one's behaviour, emotions, etc.; (countable) an instance of this.

   “I was diagnosed with Asperger's syndrome in my forties. […] Now if I am really anxious, I can take a moment to think about what is making me anxious and what to do about it; before I would just spiral into a meltdown really quickly, with no understanding of why.”

   “As the brain starts becoming overwhelmed with stress chemicals, it has two primary ways of responding. […] [I]f the accumulation of stress chemicals, stimulation and/or demands are occurring too fast or are too intense to block out, then a meltdown is probable.”

8. (Sudden) loss of control over one's behaviour, emotions, etc.; (countable) an instance of this.

   “I had a major meltdown at work today. After being instructed one more time about additional work that I was to delegate to my direct reports, I snapped, but in a very polite manner. I excused myself from the boss' office and broke down completely in my cubicle.”

   “After the huntsman raced across my windscreen, I had an arachnophobic meltdown on the side of the road.”