Initialled means to sign or mark with one's initials. Antonyms for initialled would be words that are opposite in meaning and indicate the absence of marking or signing with initials. Some possible antonyms for initialled would be erased, blank, unmarked, unsigned, untagged, unspecified, anonymous, or unrecognized. These words suggest the lack of any mark or sign that identifies and confirms the ownership or authorship of a piece of writing or an object. In contrast to initialled, antonyms imply not taking responsibility for something, leaving it open to interpretation or ambiguity.