Definition of cardinal sin
- Giving false information is a cardinal sin in news reporting.
- He committed the cardinal sin of criticizing his boss.
: cardinal number
: a crested finch (Cardinalis cardinalis of the family Cardinalidae) of the eastern U.S. and adjacent Canada, the southwestern U.S., and Mexico to Belize which has a black face and heavy red bill in both sexes and is nearly completely red in the male
: of basic importance
: very serious or grave
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