foot fault
US /ˈfʊt fɔːlt/
UK /ˈfʊt fɔːlt/

1.
falta de pie
an instance of a player serving in tennis or volleyball touching or crossing the baseline with their foot before hitting the ball
:
•
The umpire called a foot fault on the player, costing them the point.
El árbitro pitó una falta de pie al jugador, costándole el punto.
•
To avoid a foot fault, make sure your feet stay behind the line when serving.
Para evitar una falta de pie, asegúrate de que tus pies permanezcan detrás de la línea al sacar.