Italian to English Tech/Engineering Electronics / Elect Eng instruction manual

This is from instructions for a "servoazionamento", which I understand to be a "servo drive". Here's the context:

Nel motore asincrono la coppia erogata è proporzionale allo scorrimento.

I've found one possible reference on ProZ, which would lead me to believe the translation is "slip". Does anyone know for sure?

Thanks.