The term 'MAJOR WORK' can be broken down into three crossword solutions: EPIC (4 letters), OPUS (4 letters), and MAGNUMOPUS (10 letters). An EPIC is a long narrative poem, usually about heroic deeds and events that are significant to a culture or nation. An OPUS is a large and important work of art, music, or literature. A MAGNUMOPUS is an especially great or impressive work, often one that is larger or more complex than usual.