The phrase "major contribution" means a significant or important contribution. It refers to something of great value or impact that someone has given or done. Full definition
Experience working on 3rd person action / adventure games, demonstrating major contributions in the areas of hero control schemes, enemy design, navigation mechanics, and combat. (wccftech.com)
The second major contribution is the way in which his dissertation compares students in indigenous schools to indigenous students attending regular public schools. (gse.harvard.edu)
Since 1985, this annual event has recognized major contributions and emerging talents in the field. (icp.org)