A "scribal error" refers to a mistake made by a scribe or a person copying a text by hand. It could include misspellings, omissions, or other mistakes that happen during the process of writing or transcribing a document. Full definition
Save for a few scribal errors, it is completely self - consistent across all 66 books. (religion.blogs.cnn.com)
In consequence of the two tendencies and inevitable scribal errors, it becomes impossible for us to say whether the longer text or the shorter in Luke 22:19 b - 20 is the original one. (religion-online.org)
The temptation to practise exegesis by removing difficult passages, and treating them as scribal errors or the work of stupid editors, should be resisted. (religion-online.org)