An annuitant is a person who is entitled to receive benefits from an annuity.
Since 2000, in the United States of America, Federal and State agencies have allowed the re-hiring of retired employees without the loss of their retirement benefits. Such a "re-hire" is referred to as an annuitant. Often a maximum number of hours per year which the annuitant may work is specified.
This concept often allows agencies to benefit from the experience of retired employees who may be relied upon to share their experience and training with new hires, or to supplement or "bridge" areas where person power is needed but not currently affordable.