Seven Deadly Sins: Wrath

1.
Anger: From the Old Norse angr, 'sorrow', 'distress', and angra, 'to grieve'; akin to Old English enge, 'narrow', and the Germanic angst and angust, 'anxiety'; the Latin angor, 'strangling', 'tight', 'anguished', and angere, 'to distress', 'to strangle'; the Greek agkhein, 'to squeeze', 'to embrace', 'to strangle'; and the Sanskrit amhas, 'anxiety'. There is one reference, in Mark 3:5, to orges, irritation', (on the part of Jesus) in the four Gospels. There are two other references to anger in the Epistles.

2.
”To express yourself in an aggressive manner.”
Anger, or wrath, is a feeling of hostility, impatience, or rage that is often expressed in an aggressive manner. We often feel anger when we feel an injustice has been done against us, or when there seems to be no solution to a problem.
Of anger, medieval theologian Thomas Aquinas said, "A passion of the sensitive appetite is good in so far as it is regulated by reason, whereas it is evil if it set the order of reason aside." Often, anger is aimed at the wrong person or thing, which is why, along with envy and pride, it was categorized by Dante as a sin of misdirected love.
The story of Jesus and his righteousness in tossing the money-changers from the temple is often cited in discussions of anger. There is no doubt that Jesus was angry, but his anger was justified because the money-changers were defiling God's house. However, we are warned not to justify our anger with God's name lest we make him in our image rather than the other way around.
As with the sin of gluttony (in the sense of overindulgence in drink), anger becomes a sin when it causes us to lose our sense of reason, which is a gift from God. This fits well with the modern concept of anger as a loss of self-control, and a reaction to feelings of powerlessness.