The term 'become used up' can be described by three crossword solutions: ADAPT (5 letters), INURE (5 letters), and ENURE (5 letters). ADAPT means to adjust or modify something to make it suitable for a particular purpose. INURE means to become accustomed to something unpleasant or difficult. ENURE means to become established or accepted as a result of long-term use. All three words describe the process of becoming used up, either through adaptation, acclimation, or establishment.