A measure of time. The place after first. Something following. A small part, as of a minute ("just a second"). A repeating, as in a second chance. An alternate, as in every second year. Something inferior in rank ... a second vice president, a second chair in an orchestra. A standby in a duel. A gear in a car’s transmission. A reference to something or someone past … a second Pearl Harbor, a second Churchill. And the time needed for a cesium-133 atom to perform 9,192,631,770 complete oscillations.