verb

• (intransitive) To hang downward; to sag.
  "On the brown harvest tree Droops the red cherry."
• (intransitive) To slowly become limp; to bend gradually.
  "Good things of day begin to droop and drowse; While night’s black agents to their preys do rouse."
• (intransitive) To lose all energy, enthusiasm or happiness; to flag.
  "But wherefore do you droop? why look you sad?"
• (transitive) To allow to droop or sink.
  "[…] pithless arms, like to a wither’d vine That droops his sapless branches to the ground;"

noun

• (aviation) A hinged portion of the leading edge of an aeroplane's wing, which swivels downward to increase lift during takeoff and landing.

adj

• (archaic) Drooping; adroop.
  "But when the melancholy fit shall fall Sudden from heaven like a weeping cloud, That fosters the droop-headed flowers all. And hides the green hill in an April shroud :"