to break into pieces:
My poor old boots are falling apart.
If an organization, system, or agreement falls apart, it fails or stops working effectively:
The deal fell apart because of a lack of financing.
Their marriage fell apart when she found out about her husband's affair.
to experience serious emotional problems that make you unable to think or act in the usual way:
After his wife died, he began to fall apart.
(Cambridge Advanced Learner's Dictionary & Thesaurus からの fall apart の定義 © Cambridge University Press)
to break into separate pieces:
Our furniture is falling apart.
to fail completely and be unable to continue in the usual way:
The deal fell apart because of a lack of money.
When his wife died, he fell apart (= was unable to continue with life in the usual way).
(Cambridge Academic Content Dictionary からの fall apart の定義 © Cambridge University Press)
- Cambridge Dictionary