retardation

noun

1. 1

   the act of slowing down or falling behind

2. 2

   a decrease in rate of change

   the deceleration of the arms race

3. 3

   lack of normal development of intellectual capacities

4. 4

   any agent that retards or delays or hinders

   flame-retardant

5. 5

   the extent to which something is delayed or held back