Definitions for "Back-testing"
The testing of a financial model by using it on past date and then comparing the 'predictions' to what actually happened.... more on: Back-testing
The testing of a strategy based on historical data to see if the results are consistent.
A strategy is tested or optimized on historical data and then is applied to new data to see if the results are consistent.
Creating a hypothetical portfolio performance history by applying current asset selection criteria to prior time periods. Source