1a mechanical failure:breakdowns could totally disrupt production
2a failure of a relationship or system:a breakdown in military disciplinea communications breakdown [mass noun]:some of these women will have experienced marital breakdown
a sudden collapse in someone’s mental health:Heather had a breakdown following the death of her sister
3the chemical or physical decomposition of something:the breakdown of ammonia to nitrites
an explanatory analysis, especially of statistics:a detailed cost breakdown
