Letter of Mass Destruction. (noun or verb); Correspondence from one to another that typically highlights faults and vulnerabilities in the recipient. Most commonly seen as venting, although primarily used as a vehicle to communicate the un-said while involved in a relationship.
Jane: "So what finally happened between you two?"
Joe: "I just couldn't take the rejection anymore, so I LMD'd her after she walked out, telling her all of the things no one else probably ever had."