1.an abrupt failure of function or health
2.a mishap caused by something suddenly falling down or caving in
3.the act of throwing yourself down;
he landed on the bed with a great flop
4.a sudden large decline of business or the prices of stocks (especially one that causes additional failures)
1.break down, literally or metaphorically;
The wall collapsed
2.collapse due to fatigue, an illness, or a sudden attack
3.fold or close up;
fold up your umbrella
4.fall apart;
the building crimbled after the explosion
5.cause to burst;
The ice broke the pipe
6.suffer a nervous breakdown
7.lose significance, effectiveness, or value;
The school system is collapsing