A Word's a Word for A' That?

Aaron and I had a discussion awhile ago about what a "word" actually is. I said that a word must have some certain consistent definition understood by more than the person. Aaron said that any combination of syllables put together could be said to be a word. As proof he pointed out "The Jabberwocky." However, I would say that gyre and gimble and mimsy and brillig all now have meanings, or at least have concrete definitions set down by Lewis Carroll. I was going to dig out the dictionary to type the definition which is actually rather ambiguous, but I'm too lazy. So take this rambling for what it's worth....(not much =) )