footfault
/ˈfuːtˌfɔːlt/Definitions
1. noun
A fault or error in a tennis serve that touches the foot line on the service box side of the court, resulting in a let.
“The player committed a foot fault and had to replay the serve.”
2. verb
To commit a fault or error in a tennis serve that touches the foot line on the service box side of the court.
“She foot faulted on her first serve and had to try again.”