a fault consisting in the failure of the server to keep both feet behind the base line until the ball is hit or to keep at least one foot on the ground while hitting the ball.
Origin of foot fault
First recorded in 1885–90
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for foot fault
tennis a fault that occurs when the server fails to keep both feet behind the baseline until he has served
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