英和和英

Adjectiive

extra-duty (not comparable)

1. (tennis) Describing a tennis ball having a thicker felt woven more loosely around the ball's core, designed for hard court surfaces such as asphalt or concrete.
   • 2022 September 6, Matthew Futterman, “The Great U.S. Open Ball Debate of 2022”, in The New York Times‎^[1]:

     The men at the U.S. Open use what is known as an “extra-duty” ball, which means the felt on the outside of the ball is woven slightly more loosely than the “regular-duty” ball the women use. […] Extra-duty balls are the balls of choice for outdoor hardcourts, like those at the U.S. Open, except when they are not.