1 If a system, relationship, or discussion breaks down, it fails because there is a problem or disagreement. --
2 to be unable to control your feelings and to start to cry: --
3 to stop working or not be successful: --
Our car broke down on the thruway.
5 to separate, or to separate something, into smaller parts: --
Our dishwasher broke down just a month after the guarantee had expired.
If the central heating breaks down again, I will refuse to pay the repair bill.
I'm worried that his car has broken down, or worse still, that he's had an accident.
The school bus broke down and had to be towed to the nearest garage.