A plea in abatement is a type of plea that is made by certain people who are accused of a crime or a tort. In such a plea, a defendant does not deny the claim made by the plaintiff. Instead, they merely state that they disagree with the time, place or form of the accusation.
People who make pleas of abatement are generally seeking to have the action dismissed or to have it postponed due to a protocol error or problem. For example, if a person is accused of committing a crime that occurred 20 years in the past, and the statute of limitations has already expired, then they may make a plea of abatement. In such a plea, the defendant is not denying the crime, but instead saying that they can't be held accountable because the time period in which they could be held accountable has passed.