The retirement and disability program of the United States of America. May be used for similar programs in other countries. Not for use with questions unrelated to retirement or disability that might involve some kind of security.
Wikipedia says:
In the United States, Social Security is the commonly used term for the federal Old-Age, Survivors, and Disability Insurance (OASDI) program.
The tag may be used either for the US program or for similar programs in other countries (when combined with the appropriate country tag). Do not use with things related to payments unrelated to old age, survivors, or disability insurance.