noun

• The act of retarding or delaying; hindrance.
• (acoustics) The distance by which one wave is behind another.
• (music) The act of diminishing the rate of speed.
• (telegraphy) A decrease in the speed of telegraph signalling.
• The extent to which anything is retarded; the result of any retarding or delay; mental, social, or physical slowness.
• (colloquial, derogatory, offensive) Extreme stupidity.
• That which retards; an obstacle; an obstruction.
• (physics) Deceleration; reduction in the magnitude of velocity.
• (music) A suspension which resolves upwards.