Indoctrination refers to a wide range of different activities, and finding a single definition is problematic. In the fields of psychology, sociology and educational research, more precise terms are often preferred, including (but not limited to): socialization, propaganda, manipulation, and brainwashing.
In education, distinguishing (undesirable) "indoctrination" from the (acceptable) teaching of values is particularly problematic.
Religious indoctrination refers to customary rites of passage for the indoctrination of persons into a particular religion and its extended community.
Most religious groups instruct new members in the principles of the religion; this is usually not referred to as indoctrination, because of the negative connotations the word has acquired. Mystery religions require a period of indoctrination before granting access to esoteric knowledge. (c.f. Information security)
The initial psychological preparation of soldiers during training is referred to (non-pejoratively) as indoctrination. See Recruit training.
In the field of information security, indoctrination is the initial briefing and instructions given before a person is granted access to secret information.
Noam Chomsky remarks, "For those who stubbornly seek freedom, there can be no more urgent task than to come to understand the mechanisms and practices of indoctrination. These are easy to perceive in the totalitarian societies, much less so in the system of 'brainwashing under freedom' to which we are subjected and which all too often we serve as willing or unwitting instruments.
Robert Jay Lifton argues that the objective of phrases or slogans like "blood for oil," or "cut and run," is not to continue reflective conversations but to replace them with emotionally appealing phrases. This technique is called the thought-terminating cliché.