1 [no object] : to break apart and fall down suddenly
The bridge/building collapsed.
The roof collapsed under a heavy load of snow.
The chair he was sitting in collapsed.
2 a [no object] : to fall down or become unconscious because you are sick or exhausted
He collapsed on stage during the performance and had to be rushed to the hospital.
2 b [no object] : to completely relax the muscles of your body because you are very tired, upset, etc.
She came home from work and collapsed on the sofa.
The crying child ran to his mother and collapsed in her arms.
3 a [no object] : to fail or stop working suddenly : to break down completely
The civilization collapsed for reasons that are still unknown.
He warned that such measures could cause the economy to collapse.
Negotiations have completely collapsed.
3 b [no object] : to lose almost all worth : to become much less valuable
The country’s currency collapsed.
Oil prices had collapsed.
4 [no object] medical : to become flat and empty
a blood vessel that collapsed
a collapsed lung
5 : to fold together
The stroller collapses easily.
You can collapse the stroller easily and store it in the trunk of your car.
— collapsible /kəˈlæpsəbəl/ adjective
a collapsible chair/table/stroller