What is Alienation Of Affections?

Legal Definition
Alienation of affections is a common law tort, abolished in many jurisdictions. Where it still exists, an action is brought by a deserted spouse against a third party alleged to be responsible for the failure of the marriage. The defendant in an alienation of affections suit is typically an adulterous spouse's lover, although family members, counselors and therapists or clergy members who have advised a spouse to seek divorce have also been sued for alienation of affections. As of 2016, six US states (Hawaii, North Carolina, Mississippi, New Mexico, South Dakota, and Utah) recognize this tort.

The tort of alienation of affections is similar to the tort of criminal conversation.
-- Wikipedia
Legal Definition
In a minority of states, a spouse may sue a third party for purposefully interfering with the marital relationship. This suit is usually brought against the adulterous spouse's paramour. However, suit may also be brought against an in-law or relative who has advised the defecting spouse to leave the marital relationship.
Legal Definition
This the wrongful act of one person that interferes with the affection one spouse has for the other. This could be one a husband or wife is deprived of the others affection because they have fallen in love with someone else.