| poi·son-pen letter (poi'zən-pěn') n. A usually anonymous letter or note containing abusive or malicious statements or accusations about the recipient or a third party. |
poison-pen letter
A letter, usually anonymous, that makes malicious statements about the recipient or a third party. For example, She told the police about the poison-pen letters, but they said they couldn't pursue the matter. [Early 1900s]