Adjuncts are unmalted grains and other fermentables used to supplement the mash. Rice, corn, sugars added to the boil. (just to name a few)
-Priming sugar and additives like foam retention additives are definitely not adjuncts.
-I'm not so sure about flavorings like coriander. My first instinct is to say no because is doesn't supplement the mash. At least they don't add much if anything to adding fermentability.
-Fruits added to fermentation do supplement the mash albeit way downstream so... maybe they could be called adjuncts. That's another one someone else with more knowledge can elaborate on.