Jactitation:

Commenter Mike BUSL07 reminds me of a fabulous legal term — “jactitation of marriage,” “a cause of action which arises when a person falsely alleges that he or she is married to the petitioner,” R.H. Graveson, Conflict of Laws 349 (7th ed. 1974) (quoted in Black’s Law Dictionary). Few people these days engage in such misbehavior. The most recent extensive discussion I found of this in an American case comes from Sell v. Sell, 58 Mont. 329 (1920) (paragraph breaks added):

It is urged by counsel for respondent that the allegation of nonmarriage as a ground for affirmative relief is warranted by the course of procedure at common law and is in the nature of a cross-bill setting forth the grounds of complaint in an action for jactitation of marriage.

Anciently, at common law, where one person, not being married to another, pretended that a marriage existed between them and proclaimed it to others, the person against whom the claim was made, upon due proof, was entitled to a decree enjoining the offender from the false boasting. Cases of that character arose occasionally in England, but they were peculiarly within the cognizance of the ecclesiastical courts. (Blackstone, 93). The action, however, fell into disrepute in 1776, when the House of Lords in the Duchess of Kingstone’s Case (20 How. St. Tr. 543) decided that the final decree was not conclusive of the fact of nonmarriage.

In this jurisdiction the power to decree a divorce is purely statutory. (Rumping v. Rumping, 36 Mont. 39, 12 Ann. Cas. 1090, 12 L. R. A. (n. s.) 1197, 91 P. 1057.) Ample provision is apparently made by our Codes for the protection of the marital relation, and the significant fact that an action is authorized to establish marriage whenever either party to it denies the existence of the relationship (sec. 3634, Rev. Codes), tends to negative the existence of the right which is now sought to be asserted.

We think it can be said in all fairness that the right of action for jactitation of marriage has never been recognized as warranted by the common law as it was introduced in and adopted by this country.

Jactitation of screwing around, on the other hand, sounds like a cause of action with a future.