What does nonchalantly mean?

When someone is nonchalant, they act indifferent or appear unconcerned.  When a character is described as doing something nonchalantly, they are performing an action in a casual or unexcited way.  The word nonchalantly describes a verb.  The tone of an action is modified when it is described as being done nonchalantly.  It shows a level of indifference.  

In the book Maniac Magee, Giant John left a room while "nonchalantly munching" on Burger King food.  This meant that he ate the food in a way that appeared indifferent, as if he did not care about what he was eating or that he was eating at all.

Later in the book, Maniac "[gazes] nonchalantly about."  This means that he looked around in a casual way, as if to show that he did not care.