Black's Law Dictionary (2nd edition)dictionaries

Plead

To make, deliver, or file any pleading; to conduct the pleadings in a cause. To interpose any pleading in a suit which contalns allegations of fact; in this sense the word is the antithesis of “demur." More particularly, to deliver in a formal manner the defendant’s answer to the plain-tiff's declaration, or to the indictment, as the case may be

Source: Black's Law Dictionary 2nd Ed (1910)