More mentally unbalanced, erratic, or extreme than before; also used informally to mean more wild, exciting, or unbelievable.
From 'crazy,' which comes from Dutch 'kraze' or 'crasen' meaning 'to break or shatter.' The comparative form '-ier' indicates a greater degree of craziness.
The word 'crazy' has become so casual in modern speech that we barely think about its original meaning—it literally came from a word about shattering or breaking. We've softened what was once a serious term (mental illness) into a casual intensifier for anything surprising, which shows how language sanitizes difficult topics.
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