Noun
gym shorts pl (plural only)
A type of relatively lightweight shorts with elastic waistbands designed for use in sports and physical activity, especially gym class. The terms basketball shorts and mesh shorts are used nearly synonymously with gym shorts in the United States, despite their different initial usage.
She said this in the same way you might say Fields of Punishment or Hades's gym shorts. Rick Riordan
I used to sleep in the T-shirt I wore during the day and whatever ratty old gym shorts I could find on the floor. But one year for Christmas, someone gave me a very chic, comfortable pair of pajamas from Brooks Brothers, and I realized the error of my ways. Derek Blasberg