1. With no name known or acknowledged: "The anonym on the package gave rise to speculation as to who could be the anonymous sender."
2. Given, written, etc. by a person whose name is withheld: "The letter to the editor of the newspaper was signed as anonym, the authorship being withheld for a reason."
3. A name used by someone to hide his or her identity: "The ransom note was signed with an 'X' which was the anonym of the kidnapper."
4. Not easily distinguished from others or from one another because of a lack of individual features or character: "His face was a perfect anonym, very bland and undistinguished from others."