A secret agreement or plan by two or more people to do something illegal or harmful; a plot.
From Latin conspiratio, derived from conspirare (to plot together). The -tion suffix indicates the action or result of conspiring.
Both 'conspiration' and 'conspiracy' come from the same Latin root, but 'conspiracy' is far more common in modern English—showing how sometimes English keeps multiple forms from Latin, but one becomes dominant over time.
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