Responsible  adj. 1 (often foll. By to, for) liable to be called to account (to a person or for a thing). 2 morally accountable for one's actions; capable of rational conduct. 3 of good credit, position, or repute; respectable; evidently trustworthy. 4 (often foll. By for) being the primary cause. 5 involving responsibility.  responsibly adv.