1
general::
Phrase(s): 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.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Also, tail away. Diminish gradually, subside, as in The fireworks tailed off into darkness. [Mid-1800s]
American Heritage Idioms