What is Assisa Continuanda?

Legal Definition
An ancient writ addressed to the justices of assise for the continuation of a cause, when certain facts put in issue could not have been proved in time by the party alleging them. Reg. Orig. 217.
-- Black's Law Dictionary
Legal Definition
A writ granting a continuance of the assize to allow the production of papers.
-- Ballentine's Law Dictionary