well up verb 2adjective 1forms 5 verb2 •To gradually or steadily flow upwards or outwards so as to begin to fill or overflow something.Oil was welling up out of the borehole.As soon as I heard news of his death, tears started to well up in my eyes. •(figurative) To accumulate within one, to the point of overwhelming one.Emotion welled up inside me. adjective1 •(informal) Well versed; well acquainted (in or on).How well up are you on algebra? formswelled up · welling up · wells up · more well up · most well up