single word noun for somebody who is unfaithful to their spouse / relationship-partner [duplicate]

There seems to be a range of adjectives to describe such people, and the noun for such an action is infidelity, but I couldn't find a noun that can be commonly used to describe the unfaithful person.

he/she has been cheating on his/her spouse/partner, he/she is a __________

(This train of thought was prompted by somebody's garbled answer here that was giving an example involving infidelity.)

Please note: 'adulterer/ adulteress' is an obvious option, but its legal definition presupposes marriage, at least here in India, so I should like to find some other word to fit this question.


Solution 1:

To my mind the most descriptive idiom is two-timer, the noun form of two-time

- to be unfaithful to (a lover or spouse)
- to double-cross.

Solution 2:

Philanderer/ noun form to describe one who philanders

Philander [fi-lan-der] verb (used without object)

  1. (of a man) to make love with a woman one cannot or will not marry; carry on flirtations.

or

Debauchee [deb-aw-chee, -shee]/ noun

  1. a person addicted to excessive indulgence in sensual pleasures; one given to debauchery.

or

Reprobate [rep-ruh-beyt]/ noun

  1. a depraved, unprincipled, or wicked person:

Some of these terms seem to be more gender specific, but I believe that the intended application would be understood regardless of gender. Though it is anachronistic, the essence of the description could be applied to any person acting as such.