Run Rate means the result of extrapolating financial data of a period less than one year to a full year. It shows for example, how the performance of a corporation would look if current results were extrapolated out over the whole year.
Additional meaning of Run Rate:
If a firm achieved revenues of $2 million in the first quarter of the year, the extrapolated revenue is $8 million at run rate. It can be a misleading metric, especially in seasonal industries, where revenues differ a lot throughout the year.