He's always chasing rainbows with his unrealistic business ideas.
Он всегда гонится за несбыточными мечтами со своими нереалистичными бизнес-идеями.
Definitions
The phrase '(someone's) chasing rainbows' means that a person is pursuing unrealistic, unattainable, or fanciful goals or dreams, often with little chance of success.
