There isn't one! "Exempt employees" are those exempt from the overtime pay provisions of the Fair Labor Standards Act, usually known as FLSA. If you're a manager, or belong to one of the exempt worker categories such as sales employees, no time-and-a-half for you! Some employees, like farm workers, aren't covered by FLSA at all!
FLSA requires overtime pay for nonexempt employees after they have worked 40 hours in a week. But there's no definition in FLSA for "full time". So technically speaking, there's no legal definition of a full time exempt employee. In common parlance, though, it means a full time (about 40 hours per week) worker who is not entitled to overtime pay.
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