v.1. To discard or reject something: Each year the principal would cast off her role as disciplinarian and perform in the school play. The load was too heavy, so we cast it off and left it behind.
2. To let something go; set something loose: I cast off the bow line and let the boat drift in the current. The crew grabbed the lines and cast them off as the captain started the engines. The crew remained on the boat, ready to cast off at the first sign of trouble.
3. To estimate the space some manuscript will occupy when set into type: The publisher cast off the manuscript to see how long the book would be. We cast each chapter off separately in order to save time.
4. Chiefly British To secure some number of stitches in knitting and form an edge by lifting one stitch over the next: When the scarf was the correct length, I cast off. Cast off 12 stitches on the next row to make the neck edge. Make 5 stitches on the next row and cast them off.