• Ambiguity
• Lexical Ambiguity
• Polysemy

Examples and Observations:

• "The fallacy of equivocation occurs particularly in arguments involving words that have a multiplicity of meanings, such as capitalism, government, regulation, inflation, depression, expansion, and progress. . . .
  
  "To expose the fallacy of equivocation you give accurate and specific definitions of terms, and show carefully that in one place the definition of the terms was different from the definition in another."
  (Robert Huber and Alfred Snider, Influencing Through Argument. IDEA, 2005)

• "Equivocation is a common fallacy because it often is quite hard to notice that a shift in meaning has taken place. . . . The sugar industry, for instance, once advertised its product with the claim that "Sugar is an essential component of the body . . . a key material in all sorts of metabolic processes," neglecting the fact that it is glucose (blood sugar) not ordinary table sugar (sucrose) that is the vital nourishment."
  (Howard Kahane and Nancy Cavender, Logic and Contemporary Rhetoric. Wadsworth, 1998)
• "The 'warmists,' as the deniers like to call them, have been telling us for years that our rate of consumption is unsustainable and that future generations will pay a terrible price for our carelessness. If you don’t want to believe in climate change, you can argue that forecasts created by computer modeling are 'theoretical.' Or you can confuse the long-term graph of 'climate' with the short-term spikes of 'weather.' Look, there’s a snowflake! Global warming can’t be happening!
  
  "But acidification [of the oceans] permits no such equivocation. It is demonstrable, visible and measurable, and there is nothing theoretical about how it is caused or what it does."
  (Richard Girling, "The Toxic Sea." The Sunday Times, March 8, 2009)