slackener

/ˈslækənər/
noun
  1. A person or thing that makes something slower, looser, or less intense.
    • He was known as a slackener in the office, always finding ways to slow down projects.
    • The rain was a welcome slackener for the intense heat of the afternoon.
    • The new traffic light acted as a slackener, reducing the speed of cars through the intersection.
Antonyms
What does "slackener" mean? | whatsthatwordmean | whatsthatwordmean