In civil and criminal law: a plea either in abatement or in bar of an action or prosecution, alleging some new fact, and not, as in the general issue, merely disputing the ground of action or charge; compare to plead specially.
Origin
Late 16th century. From special + plea.
Definition of special plea in US English:
special plea
nounˌspɛʃl ˈpliː
In civil and criminal law: a plea either in abatement or in bar of an action or prosecution, alleging some new fact, and not, as in the general issue, merely disputing the ground of action or charge; compare to plead specially.