Liable to be required to give account, as of one's actions or of the discharge of a duty or trust: Who is responsible while their parents are away? Required to render account; answerable: The cabinet is responsible to the parliament. Involving important duties, the supervision of others, or the ability to make decisions with little supervision: a responsible position within the firm. Being a source or cause: Viruses are responsible for many diseases. Able to make moral or rational decisions on one's own and therefore answerable for one's behavior: At what age does a person become responsible? Able to be trusted or depended upon; trustworthy or reliable: a responsible art dealer. Based on or characterized by good judgment or sound thinking: responsible journalism.