1. To cause to fall or collapse.
2. To collapse due to fatigue, an illness, or a sudden attack; SYN. collapse.
3. To fail to operate correctly; to break.
4. To lose control of one's emotions; SYN. lose it.
5. To make ineffective; SYN. crush.
6. When something decomposes or reduces to its smallest parts or is reduced by someone to its smallest parts, it breaks down.