This FallaciousArgument sprung up from a misunderstanding of TautologicalDefinitionFallacy. Though FallaciousArgument is rather an understatement. It's rather an agendum around a definition and thus kind of a meta argument.

The following discussion uses the abortion rhetoric as a running example.

From TautologicalDefinitionFallacy:

[This] is the use of conveniently choosing one's own definitions to sidestep relevant issues, or to better enforce one's own rhetoric, consciously or otherwise.  E.g. in arguments on whether Abortion is wrong, I've often seen this used... where some participants define abortion thusly to prove their point: 'abortion is the murder of a person still in the womb' (conveniently sidestepping at which point an organization of human cells becomes a human and the issues with various such definitions, and using the loaded word 'murder').  This is followed with 'murder is always wrong' (which they defend by decrying and shaming anyone who might say otherwise, war and questionable definitions of 'person' notwithstanding).  Is this a problem of a tautological definition?  No, not really.  Indeed, if their definitions were ''accurate'', there'd often be no flaw in the argument.  

The only way to ''properly'' counter their sophistry is to enter a debate over definitions (which won't be well accepted by the person depending on loaded words to defend his or her position).  And LaynesLaw doesn't even really apply... ''until the definitions are hammered out, the argument hasn't even started''.  That said, I've noticed several people on this Wiki incant 'LaynesLaw' to better defend positions like those described here, essentially to prevent challenge to their questionable or loaded definitions.

I, unfortunately, lack a better name for this fallacy... but the current name irks me a little.  Maybe 'DefinitionWithAgendaFallacy'?

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This fallacy appears to be an EquivocationFallacy.  The argument starts by defining abortion as 'abortion is the murder of a person still in the womb'.  This is okay.  The fallacy occurs when they apply results from using this definition to the standard definition.

''The arguers insist that this is the 'standard definition', that there is no other, and that it is what people have always meant when they apply the word to such things as the surgical operation.  It isn't the same as the EquivocationFallacy -- using one word to mean two things at two places in one's own argument.  They mean the same thing by the word every time they use it.''  

No, they don't mean the same thing by that word every time they use it.  They may not realize they have changed definitions; they may not be willing to accept that they have changed definitions; but they have changed definitions, and this change of definitions is required for the argument to work at all.  Otherwise, the argument would apply only to killing persons in the womb, and they clearly want it to apply to the surgical procedure.
*''"Ah, but it does apply.  How else might you describe the surgical operation to murder a person in the womb but 'the murder of a person in the womb'?  Are you trying to say that babies aren't people, you horrible, horrible person?  And how dare you reduce it to 'killing' as by a hunter; abortion is premeditated, deliberated, cold-hearted, first-degree '''murder''' of a human.  If you need proof, read up on people having received sentences for two murders when the child in the womb dies along with the mother (http://en.wikipedia.org/wiki/Double_murder).  How would you explain that and hold in your fickle little mind that abortion isn't murder?"'' 
*''These people have a well-thought defense for the definition they use, and they do, indeed, mean exactly that definition when they apply it to the surgical operation.  A definition, after all, is characterized in part by providing a user the means of recognizing where the word can be used.  The only real problems with this definition is that it sidesteps a number of relevant issues (at which point does an organization of human cells become a person? is murder always wrong? etc.) and it uses lots of loaded words to better aide in shaming any opposition, which is especially useful when they shift the burden of proof to you if you wish to argue that their definition doesn't apply and plan to shame you in the process.  This sophistry involving a DefinitionWithAgenda, after all, is just a stepping stone in their overall rhetoric.  Nonetheless, it isn't really the EquivocationFallacy.''

'' 'Fallacy' includes most forms of misleading argument, including various forms of sophistry, this being why 'StrawMan' is a fallacy.  It doesn't apply only to invalid deductive argument.  Use of loaded words and twisting definitions in knots to suit your purposes certainly qualifies as sophistry, which is not 'okay'.''

Using the terms "not 'okay'" is to value the "use of loaded words" to mean more precisely:
* Wrong versus right
* unacceptable versus acceptable
* shouldn't be done versus should be done
Arguments on behalf of, or opposing, a cause, purpose, or agenda are usually loaded with such valuations. Valuations are often used to satisfy a person's position. One can not help being impressed that the valuations can and usually are used as prescriptions, guidelines, or talking points for those who would "tune in" and add them to their orchestra of "sound bytes". 

While the first bullet point does seem typical of how both sides of the issue tend to argue, that stew of AdHominem, assuming the conclusion, and RedHerring, does not change the nature of the original argument.  Its form is define the term A, show something about A, apply that result to another definition of the term A without bridging between the two terms.  That is an EquivocationFallacy. 
*The fallacy here arises not from the dictionary possessing two definitions for one term, but rather from the very nature of words as part of communication and how an agent can justify the use of a particular word to describe a particular percept or idea.  This problem can exist even if there is ''exactly'' one definition for each word.  The nature of words in communication is such that an agent or person can apply one, say "dog", when they perceive a condition that falls within a definition for that word (e.g. a furry mammal with various dog characteristics).  They then use this definition to determine characteristics that are outside their immediate perception.  In the examples provided, a person is applying the word "abortion" BASED ON THE DEFINITION that the surgeon is (with premeditation) taking a human life that exists within a womb.  Then, with this definition, they are making statements about other characteristics of the abortion... such that "it is wrong" (because murder is wrong, and murder is taking human life with premeditation).  ''There is only one definition in use.''  EquivocationFallacy cannot apply.  
*The real problem is the use of emotively loaded words as part of the definition... i.e. they use the word 'murder' in place of 'takes life with premeditation', and use the word 'person' instead of 'human life'.  It can't be reasonably argued that these alternatives aren't justifiable, but they have deeper meaning to those hearing the argument than the clinical definitions that can be used to justify their inclusion.  And that is where the Agenda comes in.

Also used in politics to confuse a party with a platform. For example, John F. Kennedy, by modern standards, is a right-wing conservative (for proof, read his inaugural address). Loose definitions (such as political left/right) invite such fallacies. This also happens when people confuse the Republican party with Conservatism (Republicans are economically left-wing), or the Democratic party with Liberalism.

Republicans and Democrats may in the broadest terms define themselves with with political positions, but to categorize them based on left/right political extremes is to neglect the fact that they all tend to identify people who they can support because they are agreeable (or less threatening) to their own interests and well-being.. The controlling agenda for voters tends to be: who will do the most for me? Granted there are those who can afford to set aside such concerns, but a great number of voters live in a world which surrounds them, not with luxury and privilege, but with limits and impositions. -- DonaldNoyes.20080524.0017.m06

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If you view the world a certain way, then generally your definitions will reflect that view. That's not necessarily evil intent; it just may be how we translate our head model to definition models. There was a similar issue on a topic somewhere on this wiki on the definition of "good driver", where the definition and one's score depended heavily on how they view driving in terms of who should do what and when.
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See FallaciousArgument