Tennis. an attendant, usually a boy or young man, employed to retrieve balls and supply players with them.
Baseball. an attendant, usually a boy or young man, who retrieves foul balls and brings the umpire new balls during the game.
Origin of ball boy
First recorded in 1900–05
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
(in sport, esp tennis) a person who retrieves balls that go out of play
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012