If you use a word pejoratively, you use it as a put-down: to show disapproval or to insult. The adverb tells you HOW the word is being used in that moment, not what the word must always mean. Someone can say 'academic' in a plain way, or pejoratively — meaning out of touch, only in books. Same spelling, different intent. This is a formal classroom and essay word. In easy talk, people say 'she said it in a rude way' or 'he meant it as an insult'. Though actually, tone, who is speaking, and who is listening all decide whether a use is pejorative; the letters on the page are not enough.