1. (usually caps.) a program of old-age, unemployment, health, disability, and survivors insurance maintained by the U.S. federal government through compulsory payments by specific employer and employee groups.
2. the theory or practice of providing economic security and social welfare for the individual through government programs maintained by moneys from public taxation.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.