Equivocation

When we construct an argument, our terms must be unambiguous.  Their meanings must be clear and known to all involved.  Politicians and sophists of various stripes love to exploit ambiguity.  This is a fallacy known as equivocation.

Consider the following bit of dialogue:

Are you aware that Jim is gay?
Really?  He doesn't seem that happy to me.

The ambiguous term gay here is exploited by the meanings homosexual and happy, carefree.

Another example in the form of a syllogism:

God is love.
Love is blind.
Therefore God is blind.

This argument is valid, but is not sound because the terms love and blind are ambiguous.  Their meaning changes throughout the syllogism, and the multiple meanings of the words are exploited.  The first love refers to love of a self-sacrificing the nature, the second to erotic love or sacrificial love, depending on whom you're talking to.  The first blind is metaphorical, whereas the second is literal.  Arguments like this are sound and fury signifying nothing.