1.
( of a machine or vehicle ) to stop working because of a fault :
The telephone system has broken down.
We (= the car) broke down on the freeway.
—related noun breakdown
2.
to fail :
Negotiations between the two sides have broken down.
—related noun breakdown
3.
to become very bad :
Her health broke down under the pressure of work.
—see also nervous breakdown
4.
to lose control of your feelings and start crying :
He broke down and wept when he heard the news.
5.
to divide into parts to be analysed :
Expenditure on the project breaks down as follows: wages $10m, plant $4m, raw materials $5m.
—related noun breakdown