adjective

• Delayed; delayed in development, hindered; impeded.
• (psychology, sometimes offensive, dated) Having mental retardation; mentally deficient or underdeveloped.
• (psychology, sometimes offensive, dated) Specifically, having an IQ below 70.
• (colloquial, derogatory, offensive) Extremely stupid.
• (physics) Designating a parameter of an electromagnetic field which is adjusted to account for the finite speed of radiation.