As a counter example, I was greatly unnerved the other day at watching a bar discussion between two friends that revolved on whether or not one could make money daytrading. Friend A said "obviously you can't, the market is random", while friend B insisted that "well, with mathematics you can predict the way it will go". This went on for hours (I refused to join) while they both had clearly very different meanings for the words "random", "luck" and "mathematics". I believe that, had they stopped early enough to define those terms, they wouldn't have argued.
Of course, sometimes the discussion is specifically about the definition of a few key words. Even then, I find what really helps is agreeing on some restricted definitions for other "primitive" words and using those primitives to build up definitions for the words in question. For example, person A could argue that selfishness is actually a form of blindness, while person B insists that it is not really so, and one can be selfish while seeing what others are doing. This way they can argue, by having pre-defined what "blind" "see", etc mean in this context.
Discussions about the meaning of words are easily just philosophical traps where one person says A and the other hears B.
Keep pulling and you have two options. You can base things on what you observe, which leads to science, or what you on things you assume which leads no where when others don't agree to the same assumptions. It's only when people have the same assumptions that you can have really interesting discussions such as Math or a good logic puzzle.