Equivocation is the use of a word with more than one meaning in an argument.
This Abbot & Costello sketch is a non-stop exercise in equivocation:
The Principle of Charity
The Principle of Charity is the principle that we should choose a positive interpretation of what someone is communicating when it is ambiguous.
The following video gives some good examples of situations when this principle is needed!
How should the Principle of Charity be applied to the dispute in this video?