Longman Dictionary of Contemporary English - possibly

~ adv 1 used when saying that something may be true or likely, although you do not know exactly; perhaps  ("Are you coming with us tomorrow?" "Possibly. I'm not sure yet." | This novel is his most accessible, and possibly his most beautiful, book. | quite possibly (=used to say that something is very likely))  ("Do you think it was murder?" "Quite possibly.") 2 could you possibly/can you possibly spoken used when making a polite request  (Could you possibly lend me another $ till Monday?) 3 spoken used to say that you are very surprised or shocked by something, or you cannot understand it  (can/could sb possibly)  (What on earth can she possibly mean? | How could anyone possibly do such a thing?) 4 used to emphasize that someone tried as hard as they could to achieve something  (do everything you possibly can/could)  (Doctors did everything they possibly could to save the little boy's life.) 5 sb can't/couldn't possibly used to say strongly that you refuse to do something or that someone cannot do something  (I can't possibly allow you to go home in this weather.)