foot' fault" Tennis.
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.
foot•faultPronunciation: (foot'fôlt"), [key]
to commit a foot fault.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.