(Latin: ango, distress)
A strongly exciting emotion aroused by an evil that is present but not acquiesced in.
Though commonly a self-regarding emotion, it may be aroused in behalf of others.
Anger is not purely painful as it includes the agreeable consciousness of energetic reaction against evil, and is not of itself morally evil, but may be at times a high moral force in the form of virtuous indignation, called "just" anger.
It needs restraint as it can easily become inordinate and lead to a purpose of revenge or pass into hatred and it is then a vice.
New Catholic Dictionary