This is the 7928th most frequent Russian word.
кит
Whale.
Here, 'кит' refers to the animal whale, used as the subject of the sentence.
Кит плавает в океане.
The whale is swimming in the ocean.
In this case, 'кит' is used metaphorically to describe someone influential or important.
Этот человек — настоящий кит в бизнесе.
This person is a real big shot in business.
The word 'кит' appears in its general zoological context to identify the animal species.