Originally Posted by
Buffalobiian
You start pretty much ALL arguments with definitions. Debating is done that way too, by defining the topic when you're First Affirmative. First Negative may accept or reject their definition.. but as yourself and shinta have alluded to.. it doesn't make for much of an argument afterwards when you go into definition-arguments since it becomes A-says-but-B-says.
But in your case, and in general, my favourite (and instinctive) move is always to ask them to clarify or explain their definitions. Not only does it clear out any misunderstandings, but when/if they say something really stupid it lets you attack them first. After you make them look stupid (usually from contradicting themselves), THEN you make your argument (if you're supposed to).
I have so much fun tearing people apart it's almost sadistic.