lounge suit

a man's suit appropriate for informal occasions.

Origin of lounge suit

First recorded in 1900–05

To this officer a sack-suit or business-suit is a lounge-suit.

The American Language |Henry L. Mencken
The lounge-suit that he was wearing might serve, but his luggage was totally impossible.

The Regent |E. Arnold Bennett
"I presume you'll dine up here, sir," said Joseph, glancing at the lounge-suit.

The Regent |E. Arnold Bennett
Yet I stood aghast, for with the lounge-suit of tweeds I had selected the day before he had worn his top-hat!

Ruggles of Red Gap |Harry Leon Wilson

On one occasion, too, he appeared in the trousers of a lounge-suit of tweeds instead of his dress trousers, and with tan boots.

Ruggles of Red Gap |Harry Leon Wilson

lounge suit

the customary suit of matching jacket and trousers worn by men for the normal business day