What is the meaning of falling 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, drop-off, falloff

verb

• Come off.
  • usage: "This button had fallen off"
  • synonyms: fall off
• Fall heavily or suddenly; decline markedly.
  • usage: "The real estate market fell off"
  • synonyms: slump, fall off, sink
• Diminish in size or intensity.
  • synonyms: fall off, fall away