a cornered rat will bite the cat; desperate people fight back fiercely
A yojijukugo proverb meaning that even the weak will fight back desperately when cornered. Often used to warn against pushing someone too far.
See also: 窮鼠猫を噛む
If you corner him too much, he might do anything—a cornered rat will bite the cat.
This is the full proverbial form; 窮鼠噛猫 is a compressed yojijukugo version with the same meaning.
A yojijukugo derived from the Chinese proverb 'a cornered rat will bite the cat' (窮鼠噛猫). The Japanese form compresses the longer phrase 窮鼠猫を噛む into four characters.