The term 'gradually disappear' can be described by four different crossword solutions: EVANESCE (8 letters), FADE (4 letters), FADEOUT (7 letters), and wearoff (7 letters). EVANESCE means to vanish gradually, while FADE means to become less distinct or visible. FADEOUT is a gradual decrease in sound or image intensity, and wearoff is the gradual disappearance of an effect. All of these words describe the process of something gradually disappearing.