tail off
To dwindle, diminish, or fade away; to become fainter or weaker. His campaign started really strong, but public support for the candidate tailed off following a series of scandals. The lights on the car began tailing off into the blackness of the night, leaving me alone in the empty field. He started talking about the tax code, but he tailed off when he realized no one was listening.
tail off
to dwindle to nothing. The number of people filing for unemployment insurance is beginning to tail off. As the storms tailed off, we began to realize how much damage had been done.
tail off
Also, tail away. Diminish gradually, subside, as in The fireworks tailed off into darkness. [Mid-1800s]