What is Nonissuable Plea?

Legal Definition
Those upon which a decision would not determine the action upon the merits, as a plea in abatement 1 Chit. Archb. Pr. (12th Ed.) 249.
-- Black's Law Dictionary
Legal Definition
the term that is given to the defence that raises no issue of the facts in the case.
Legal Definition
A plea not going to the merits, e. g., a plea to the jurisdiction.
-- Ballentine's Law Dictionary