What is the meaning of drop-off?

noun

• A noticeable deterioration in performance or quality.
  • usage: "the team went into a slump"; "a gradual slack in output"; "a drop-off in attendance"; "a falloff in quality"
  • synonyms: slump, slack, falloff, falling off
• A steep high face of rock.
  • usage: "he stood on a high cliff overlooking the town"; "a steep drop"
  • synonyms: cliff, drop
• A change downward.
  • usage: "there was a decrease in his temperature as the fever subsided"; "there was a sharp drop-off in sales"
  • synonyms: decrease, lessening