Fade out is a term used to describe a gradual reduction in intensity or volume, often referring to a gradual reduction in sound or light. However, there are several synonyms for this term that you can use depending on the context and application. For instance, you may use the phrase "diminish slowly" or "taper off" to describe a fading-out sound. You may also use "dissolve" or "vanish gradually" to depict a fading-out visual effect. Other synonyms include "weaken," "die away," "ebb," "recede," "trail off," or "decrease gradually." Choose the right synonym for your intended effect and improve your language skills.