very like a whale

Adjective

humorous not-comparable slang

(slang, humorous) Highly improbable; not to be believed.

Japanese Meaning

非常にありえない、信じがたい / ばかげた、突拍子もないほど非常識

The idea that he'd finish the novel in a week is very like a whale.

彼が1週間で小説を仕上げるという考えは、まずありえない。

Sense（1）

(slang, humorous) Highly improbable; not to be believed.