The term 'untighten' is a verb meaning to RELAX or make less tight. It is often used in reference to physical objects, such as loosening a knot or untightening a screw, but it can also be used figuratively to describe a situation or emotion. The crossword solution for this term is 'RELAX', which is a verb meaning to become or make less tense or anxious. This term is often used to describe a person's mental state, and can also be used to describe a physical object that has been made less rigid.