downer

/ˈdaʊnər/
noun
  1. Something that makes you feel sad, depressed, or disappointed.
    • The rainy weather on vacation was a total downer.
    • I don't want to be a downer, but we need to talk about the budget cuts.
    • The news about the canceled trip was a real downer.
  2. A drug that slows down the body and mind, such as a sedative or tranquilizer.
    • She was prescribed a mild downer to help her sleep.
    • The doctor warned him not to mix downers with alcohol.
    • Abusing downers can lead to serious health problems.