There are no state or federal laws that define "full time" or "part time" employment. Employers may legally schedule their employees for any number of hours per week and call those schedules "full time" and/or "part time" as they see fit.
For example, your employer can schedule you for two hours per week and call you a full time employee, and schedule your coworker for 60 hours per week and call him/her a part time employee, and this would be perfectly legal.
If you're not asking about legal definitions of "full time" and "part time" (because, as I said above, there aren't any), but rather your benefits providers' definition of "full time" and "part time" then we have no way of knowing this. Every benefits provider has a different definition of these terms, and every definition is legal. To determine what your provider's definition is, you'll have to contact your benefits provider directly.