From The Art and Popular Culture Encyclopedia
Indignation is an emotion, and is considered to be a type of anger. Indignation is often composed of anger, disgust, contempt, and resentment. Simply, indignation can be defined as anger that is caused by something that is unfair or wrong. Indignation is an attribution-related emotion causing this emotion to be very personal to those experiencing it. Indignation has been described as the opposite emotion to respect even though it has become synonymous with anger, whose opposite is gratitude, in the modern English usage.
The word indignation stems from the 1200th century Old French word indignatio. This Old French word comes directly from the Latin word indignationem. In nominative form, indignationem is indignatio, meaning displeasure. Indignatio is a noun of action from the past participle stem of indignari. Indignari’s meaning is to regard as unworthy or to be angry or displeased at. Indignari comes from the word indignus, meaning unworthy. Opposite of the word dignus, meaning worthy.
Indignation is perceived by many as a word that is exchangeable with anger. The two terms have been viewed as very similar because they are related. The main difference between indignation and anger is that indignation is a type of anger that stems from a very specific event-based cause. Indignation has not been researched that much by itself because it is so closely associated with anger. It has been stated that, “An extensive literature search has not produced a single coherent definition of indignation."