The word "aroma" was traditionally used to describe the smells derived directly from the grapes used to make a wine (e.g., "raisiny" or "earthy"), as opposed to "bouquet," which refers to the overall smells that come about as a result of the aging process (e.g., "oaky" or "charred"). These days, however, aroma is more commonly used to describe a wine's entire range of smells, and bouquet has become more or less a synonym for aroma. If you want to get into an argument with a wine purist, defining aroma is a good place to start.