What is Assise Of Fresh Force?

Legal Definition
In old English practice. A writ which lay by the usage and custom of a city or borough, where a man was disseised of his lands and tenements in such city or borough. It was called "fresh force," because it was to be sued within forty days after the party's title accrued to him. Fitzh. Nat. Brev. 7 C
-- Black's Law Dictionary