Meaning of (A CASE OF) DOG EAT DOG in English

(A CASE OF) DOG EAT DOG

a situation in business, politics, etc. where there is a lot of competition and people are willing to harm each other in order to succeed :

I'm afraid in this line of work it's a case of dog eat dog.

We're operating in a dog-eat-dog world.

Oxford Advanced Learner's English Dictionary.      Оксфордский английский словарь для изучающик язык на продвинутом уровне.