Tail-off is a commonly used phrasal verb that is used to indicate a decrease or diminishment in the intensity, amount or speed of something. Some synonyms for tail-off include decelerate, decline, dwindle, ebb, fade, peter out, recede, taper off, wane and abate. All these synonyms highlight the gradual reduction in something and the decreasing of its importance and significance. The usage of these synonyms may vary based on the context. For example, the word ebb is mainly used to describe the decrease in the tide while wane is used to describe the waning of the moon. Therefore, using these synonyms instead of tail-off can make your writing more varied and interesting.