- To unfasten, undo, or untie a cable, line, or sail.
In knotwork, a bend is a type of knot used to join two lengths of rope. Therefore, to unbend something is to untie it.
King, D., Hattendorf, J.B, & Estes, J.W. (1997). A Sea of Words: A Lexicon and Companion for Patrick O’Brian’s Seafaring Tales (2nd Ed.). Owl Books.