taper off

verb

Etymology: From taper and off.

1. To diminish or lessen gradually; to become or make smaller, slower, quieter, etc.

   “Months after they printed the article, the number of angry letters finally started to taper off.”

   “The traffic tapers off towards mid-May, but it continues in some measure throughout the off-peak months.”

2. Used other than figuratively or idiomatically: see taper, off.

   “The glass tapers off at the top.”