In the book Catching Fire Katnisse's  acts of defiance results in going back in to the arena with Peeta.

an act of defiance is when someone goes against authority Katniss hung a dummy with cinnica cranes name on it..peeta painted a picture of Rue's dead body with the flowers all. the Tributes held hand and stood in unity. this is defiant because they are supposed to be against each other. in their interviews they talked about president snow caring and how its his fault this is happening. This is an attempt to get people to rebel cinna was rebellious because he made katniss look like a Mocking-jay when she was at the Tribute Interview. i thank katniss was most defiant because she hung a dummy and painter cinnicas name on its chest.