Woolf decoded

Yes, he [Peter Walsh] remembered Regent’s Park; the long straight walk; the little house where one bought air-balls to the left; an absurd statue with an inscription somewhere or other.

—Virginia Woolf, The Annotated Mrs. Dalloway (2021) (p. 82), notes by Merve Emre

air-ball turns out to be a bit of a disappointment. I was hoping that it meant a tasty treat. But big Oxford has “a ball inflated with air, a toy so called.” Also it appears to be a Briticism that has fallen out of use. Webster II doesn’t have an entry, nor does my Concise Oxford of 1990.

And, of course, nothing to do with a missed shot, although I suppose you could launch an air ball with an air-ball.