A more thorough explanation:

Definition: Assignation refers to:

1. An appointment made to meet someone, especially for engaging in sexual activity, which is an old-fashioned usage of the term.
2. A specific allegation made by a defendant in response to a plaintiff's complaint in ecclesiastical law.
3. A plaintiff's complaint or a writ of summons in French law.

Examples:

• He made an assignation with his lover at the hotel.
• The defendant's assignation in his counterpleading was dismissed by the court.
• The assignation filed by the plaintiff was accepted by the court.

The first example illustrates the old-fashioned usage of the term assignation, where it refers to a secret meeting for sexual activity. The second and third examples illustrate the legal usage of the term assignation, where it refers to specific allegations made by the defendant or the plaintiff in a legal case.