an abrupt failure of function or complete physical exhaustion
"the commander's prostration demoralized his men"
a natural event caused by something suddenly falling down or caving in
"the roof is in danger of collapse"
"the collapse of the old star under its own gravity"
The act of collapsing.
"The sudden collapse of the roof left everyone inside trapped in darkness."
collapse due to fatigue, an illness, or a sudden attack
"After running the marathon, he collapsed from sheer exhaustion."
fall apart
"the building crumbled after the explosion"
"Negotiations broke down"
lose significance, effectiveness, or value
"The school system is collapsing"
"The stock market collapsed"
To break apart and fall down suddenly; to cave in.
"The old bridge collapsed into the river below when a heavy truck drove across it."
In plain English: To collapse means to fall down suddenly and completely, often because something is too heavy or weak to stay up.
"The old bridge suddenly collapsed under the weight of the heavy truck."
Usage: Use collapse when something breaks under pressure or falls inward, such as a building caving in during an earthquake. Do not use it interchangeably with crumble unless the subject is soft material like bread drying out rather than a solid structure failing instantly.
The word comes from the Latin collapsus, which is the past participle of collabor. It originally described something that had fallen together or in upon itself.