A book containing models of handwriting for learners to imitate. The teacher handed out a copybook to each student to practice their cursive writing.
A book used for writing exercises or notes, often used by students. She filled her copybook with notes from the history lecture.
In computing, especially in COBOL, a reusable file or section of code containing data descriptions that can be included in multiple programs. Before compiling, she updated the copybook to reflect the new database schema.