The term 'TO BOW' is used to refer to the technique of playing a stringed instrument, such as a violin or cello. The two crossword solutions, ROSIN (5 letters) and ARCO (4 letters), are both related to this technique. ROSIN is a sticky substance that is applied to the bow of the instrument to increase friction and create a better sound. ARCO is a musical term that refers to the technique of playing with the bow. Together, these two solutions help to explain the term 'TO BOW'.