Tying up, which refers to the act of securing or fastening an object, can be expressed using various synonyms. One such synonym is "binding," which entails the use of ropes, tapes, or cords to hold objects together. "Lashing" is a similar term that involves securing an object using fastened ropes or straps. Another synonym for tying up is "knotting," which involves tying a rope or cord in a loop to secure it in place. One can also use "fastening" or "attaching" to describe tying up an object. Overall, many synonyms exist for the term tying up, each with slightly different connotations, depending on the context and desired effect.