brain ‧ wash /ˈbreɪnwɒʃ $ -wɒːʃ, -wɑːʃ/ BrE AmE verb [transitive]
to make someone believe something that is not true, by using force, confusing them, or continuously repeating it over a long period of time:
Young people are being brainwashed by this religious group.
brainwash somebody into doing something
Commercials brainwash consumers into buying things they don’t need.
—brainwashing noun [uncountable]