A domineering, forceful, or assaultive verbal or physical action toward another person as the motor component of the affects of anger, hostility, or rage. [L. aggressio, fr. aggredior, to accost, attack]
* * *
ag·gres·sion ə-'gresh-ən n hostile, injurious, or destructive behavior or outlook esp. when caused by frustration
* * *
ag·gres·sion (ə-greshґən) [L. aggressus, from ad to + gradi to step] a form of behavior which leads to self-assertion; it may arise from innate drives and/or a response to frustration; it may be manifested by destructive and attacking behavior, by covert attitudes of hostility and obstructionism, or by a healthy self-expressive drive to mastery.Medical dictionary. 2011.