Ok, I did a bit of reading... it seems that the Surgeon's General stated that the reason they did not rely on one single study to support the addictive nature of nicotine was that there was a discrepancy in the definition of "addiction." But, literally thousands and thousands of studies were submitted and used for the decision; therefore, one single study was not used, but thousands of accumulated studies. This one phrase seems to be the catch all for the deniers.
This is like saying that scientists could not agree on the term "round." (a perfect sphere or how far from deviation of perfect will we accept?) However, we have huge amounts of studies, personal experiences, histories, and explorations to say that it is in fact "round" to the degree that we all accept the term in our understandings.
If you just want to win an argument for the sake of doing so, getting nitpicky about the definition is up there with arguing whether oral sex is in fact sex. It's not doing anyone any good, unless you just want a technicality, like this is a game or something.
But, it is safe to say that world-wide evidence, testing, experiences, cultures, and every conceivable human endeavor will show that nicotine is addictive. "Addictive" as defined by what we all pretty much know the word to mean. Now, if some university wants to definee the term, that is in their interest for some scientific reason, pending how the study is to be used or further studied, but doesn't negate the universe of evidence that supports the fact that it is indeed addictive.