To persist in doing something; to continue to repeat an action after the original stimulus has ended.
To cause the perseveration of (a given reflex or response).
To aim for, go after (a specified objective, situation etc.).
To follow, travel down (a particular way, course of action etc.).
To follow urgently, originally with intent to capture or harm; to chase.
To participate in (an activity, business etc.); to practise, follow (a profession).
To act as a legal prosecutor.