Social Security tax is a term used to refer to the contributions or deductions made by employees and employers to the Social Security program. However, this term also has synonyms that can be used to describe the same concept. These synonyms include FICA tax, payroll tax, and OASDI tax. The FICA tax or Federal Insurance Contributions Act tax is the employee and employer tax contribution to Social Security and Medicare programs. The payroll tax, on the other hand, is a general term used to refer to the Social Security and Medicare taxes calculated based on employee wages. Lastly, OASDI tax stands for Old Age, Survivors, and Disability Insurance tax and is another term used to describe Social Security tax contributions made by workers and employers.