Disappointed by discovering that someone or something is not as good or admirable as you believed; losing faith or hope.
From 'dis-' (reverse, negate) + 'illusioned' (having illusions). The word means literally 'freed from illusion,' coined in the 1800s though the concept is ancient.
After World War I, an entire generation called the 'Lost Generation' became disillusioned with their governments and societies, and their writings created a cultural standard for what betrayed idealism looks like.
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