smoking jacket

WordReference Random House Unabridged Dictionary of American English © 2025

smok′ing jack′et, 

1. Clothing a loose-fitting jacket for men, often of a heavy fabric and trimmed with braid, worn indoors, esp. as a lounging jacket.

• 1875–80

Collins Concise English Dictionary © HarperCollins Publishers::

smoking jacket noun

1. a man's comfortable jacket of velvet, etc, closed by a tie belt or fastenings, worn at home

Etymology: so called because it was formerly worn for smoking