'owzat! or Howzat! was an exclamation heard on the cricket ground. It was once heard, for instance, when the Fifth Doctor was playing in a Stockbridge Cricket Club match. (COMIC: The Tides of Time) Later, the Doctor said it rhetorically after he used a gigantic ball to effectively bowl over a couple of Tractators on Frontios. (TV: Frontios)
Behind the scenes
Although never defined in DWU, it was simply a general interjection used by fielders to attract the attention of an umpire, in the hopes that a call might be reversed.