When a critical mistake is discovered after a book is printed, the publisher may order the offending page to be cut out and a corrected leaf tipped in its place. The new, corrected page is called a cancel, while the removed page is the cancellandum. This process avoids the massive expense of reprinting the entire signature or volume.
Heard on the job
We found a massive libel issue in chapter four, so we've to print a cancel and manually paste it into the whole run.