1. delayed or slowed in development or progress
Usage: formal; technical
2. having an intellectual disability
Usage: dated; now considered offensive; replaced by terms like ‘intellectually disabled’

Examples

• The plant’s growth was retarded by the lack of sunlight.
• Cold weather retarded the construction project’s progress.
• The medication retarded the spread of the infection.
• Economic development was retarded by political instability.
• Fire retardant chemicals retarded the flames’ advance.
• The term ‘mentally retarded’ is no longer used in medical contexts.