Definition of new ball in US English:

new ball

noun

Sport
  • A previously unused ball, specifically one brought into use in cricket at the beginning of an innings or after a prescribed number of overs, or in tennis after a specified number of games.

Origin

Early 20th century; earliest use found in E. M. Forster (1879–1970), novelist and essayist. From new + ball.

Pronunciation

new ball

/ˌnjuː ˈbɔːl/