verb
to teach (someone) to fully accept the ideas, opinions, and beliefs of a particular group and to not consider other ideas, opinions, and beliefs
(source-Merriam-Webster)
I encounter this word in the reading “The virtue of idleness”. The word is found in the sentence “Parents begin the brainwashing process and then school works yet harder to indoctrinate young people with the necessity of early rising.” After I look it up in the dictionary, I now understand it means to teach someone to fully accept the ideas.
Don’t forget about the second part of the definition: “to not consider other ideas, opinions, and beliefs.” You might look up brainwashing as well to have a better idea of the tone of the meaning–it’s not positive.