1. the quality or state of being deceptive or dishonest; the tendency to mislead or trick others
Usage: uncountable noun; formal register

Examples

• The deceitfulness of his promises became clear when he failed to deliver.
• She was shocked by the deceitfulness hidden beneath his charming smile.
• The company's deceitfulness in advertising led to a lawsuit.
• His deceitfulness made it impossible for anyone to trust him.
• The deceitfulness of the scheme was eventually exposed by investigators.
• Parents warn children about the deceitfulness of strangers online.