1. below normal or average in quality, ability, or performance
2. having intellectual abilities significantly below average
Usage: clinical; potentially offensive when used casually

Examples

• The test results showed subnormal performance in several areas.
• Subnormal temperatures were recorded throughout the winter.
• The patient exhibited subnormal cognitive function after the injury.
• His subnormal vision required corrective lenses.
• The crop yield was subnormal due to the drought.
• Medical professionals avoid using ‘subnormal’ when discussing intellectual disabilities.