v.1. To diminish gradually; dwindle or subside: The singer's voice tails away at the end of the song. The fireworks tailed off into darkness.
2. Sports To veer from a straight course. Used of a ball that has been hit or thrown: The pitcher snapped his wrist when throwing the ball, and it tailed away as it approached home plate. The wind caused the football to tail off and the receiver couldn't catch it. The uneven table caused the pool ball to tail off.