1. Subtle and cumulative harmfulness (especially of a disease) 
2. The quality of being designed to entrap

Derived forms: insidiousnesses

See also: insidious

Type of: harmfulness, injuriousness, perfidiousness, perfidy, treachery

• appro
• approach
• approach path
• approach pattern
• approach shot
• approach trench
• approachability
• approachable
• approaching
• approbate
• approbation
• approbative
• approbatory
• appropriable
• appropriate
• appropriately
• appropriateness
• appropriation
• appropriation bill
• appropriative
• appropriator
• approval
• approve
• approved
• approver