Pleading over refers to a pleading by the defendant in a criminal case after the overruling of a plea by him/her not going to the merits of the case, such as a plea in abatement. It means serving or filing an amended pleading after an attack by one's adversary upon his/her pleading. It is a pleading to the facts after demurrer overruled.
Pleading over to a declaration adjudged good on demurrer, without any reservation, is a waiver of the demurrer. [Watkins v. United States, 76 U.S. 759 (U.S. 1870)].
The following is an example of a state statue (Washington) on pleading over:
Rev. Code Wash. (ARCW) § 10.40.100. “If the motion to set aside the indictment [or information] be denied, the defendant must immediately answer the indictment or information, either by demurring or pleading thereto.”