1. A violent action that is hostile and usually unprovoked: So many children in school have shown aggression and anger on the playground by hitting back when pushed accidentally by other children during a game.
2. Deliberately unfriendly behavior: Sometimes aggression is shown by some football fans when their team loses a game and they verbally attack the supporters of the winning side.
3. The act of initiating hostilities: Because Timmy wasn’t happy at home, he turned his aggression towards the other kids at school by pushing them, taking their ball away from them during a game, or calling them bad names.
4. A disposition to behave contentiously or offensively: James had a very unhappy childhood while he was living in a bad environment and so he expressed feelings of aggression when dealing with other people.
5. A feeling of hostility that arouses thoughts of attack: A sensation of aggression developed in Jerry when he was falsely accused of stealing money from a woman's purse at a restaurant.
6. Etymology: from ad-, "to" + gradi, gressus, "to step"; from gradus, "a step".