(Fewer Than) 50 Ways to Leave Your Lover

Definition - to release oneself from marriage

Unmarry is most often encountered in the adjective unmarried, a word that may describe either a person who has been previously married or one who just couldn't yet be bothered to indulge in matrimony. The verb may be used in both a transitive manner ('I unmarried my spouse') or intransitive ('we married and unmarried the same day').

However 'tis, I now think fit to unmarry 'em; 
And as for him, I'll use him with what Rigor, 
The utmost limits of the Law allows me.
— Aphra Behn, The Town-fopp, 1677

Definition - to run away from one's husband with a lover

For many of us the word elope conjures up dramatic imagery of forbidden love and excitement, young lovers fleeing parental disapproval in order that they might marry. In this context the verb is often found paired with the preposition with. However, the word has another, related, sense, in which at least one party (in addition to parents) is not very happy. This is the sense in which a woman leaves her husband for her lover (and is typically paired with the preposition from).

Also for a man that liueth asunder from his wife, there lyeth Action in a Court Ecclesiastical, for him to receiue her againe and to cohabite with her; as may be gathered by that statute of Westminster the second; where it is prouided; that a woman eloped from her husband, shall loose her dower: except the husband (without compulsion Ecclesiasticall) doe receiue her againe.
— Richard Cosin, An Apologie for Svndrie Proceedings by Jurisdiction Ecclesiasticall, 1593

MORE ELOPE HISTORY: The Changing Meaning of 'Elope'

Definition - to abruptly cut off all contact with (someone, such as a former romantic partner) by no longer accepting or responding to phone calls, instant messages, etc.

This sense of ghost is by far the youngest of the words on this list. It still has that new word smell, a subtle bouquet formed of a speaker's youthful irreverence for the language and a listener's incomprehension at hearing an unfamiliar term. Ghost needn't be restricted to describing leaving a romantic interest; one may ghost a social situation, such as a party, or anyone with who one has a social connection. One of our earliest examples of its use comes from a thread in a Usenet group (rec.sport.golf) from 1996, titled "My instructor 'ghosted' me...should I lose the bum?"

Definition - to get rid of unceremoniously or irresponsibly

Dump is also a relatively recent addition to our catalogue of ways to describe the ending of a romance. The initial uses of this sense of the word appear to have been more often political in nature; a politician dumped by his or her own party, or a labor leader dumped by the union. In the middle of the 20th century the English-speaking people realized its applicability in referring to the action of brusquely declaring 'it's over.'

There is a father, Vilmos, but he showed signs of character and was dumped by his woman a long time ago.
— Register Mail (Galesburg, IL), 26 Sep. 1960

Definition - to end a romance

Break up has been in use as a verb, with a large number of possible meanings, for many hundreds of years. Our earliest record of the word meaning "to end a romance" comes from a 1702 translation of a book about the happenings in the French court (quelle surprise).

For that very day she made a show of melancholy to the Duke; she told him that she could no longer converse with him, as hitherto she had done; because her conscience reproached her continually with her guilt, and represented to her every moment, that she only was the cause that he abandoned his Lady the Dutchess; and that every body blamed her for it, as no doubt she deserved to be, insomuch that there was nothing but that one consideration, she was obliged to tell him, that he must resolve to break up with her, since their converse was equally shameful, and sinful to them both.
— Marie Catherine de la Motte (trans.), Memoirs of the Court of France, 1702

Oddly enough, this sense appears to have seen little to no use for almost two centuries following, and did not enter into common use until the end of the 19th century.

Definition - a letter (as to a soldier) in which a wife asks for a divorce or a girlfriend breaks off an engagement or a friendship

The name John has been saddled with several unfortunate meanings over the years, including "toilet" and "a prostitute's client." To these we may add "recipient of a breakup letter." The epistolary john seems to have entered our lexicon during the Second World War.

A "dear John" letter, in case you didn't know, is one received by a soldier overseas from his girl, who says she is marrying a 4F, or a wife who says she would like to divorce him.
— Knoxville News-Sentinel (Knoxville, TN), 21 Mar. 1944    

Definition - a state of romantic estrangement or dissolution

The noun suffix -ville has long been added to existing words, with the meaning of "place, category, or quality of a specified nature." Typical examples of this construction are dullsville, squareville, and Hooverville. In the early 1950s the sense of split meaning "to sever relations" was added onto -ville, providing unhappy couples with a moderately undignified word with which to describe their state of emotional disengagement.

James Farrell and wife, Hortense Alden, reported in Splitsville.
— Earl Wilson, The Morning Herald (Uniontown, PA), 9 May 1951