A machine built as an induction motor and driven above synchronous speed, thus acting as an alternating-current generator; -- called also asynchronous generator. Below synchronism the machine takes in electrical energy and acts as an induction motor; at synchronism the power component of current becomes zero and changes sign, so that above synchronism the machine (driven for this purpose by mechanical power) gives out electrical energy as a generator.  [Webster 1913 Suppl.]