Side-Slipper

A person who will initiate and wishes to, or attempts, to become involved, usually romantically, with a man or woman, who is already in an established relationship, (e.g., married, engaged, boyfriend/girlfriend, etc.), but will not put forth the effort to obtain and establish a relationship of their own. To engage in an affair or come between two parties. Such relationships might be deemed genuine, at least from the perspective of the "side slipper," or merely an attempt by such a person to interfere with the sole purpose of causing temporary or permanent disruption of the established party's relationship. (May also be seen or written as "Side Slipper"). Variation: To "side-slip."