diːsɛləˈɹeɪʃən dɪˌsɛləˈɹeɪʃən læɡ ˌsʌbnɔːˈmælɪtɪ the act of slowing down or falling behind a decrease in rate of change the deceleration of the arms race lack of normal development of intellectual capacities any agent that retards or delays or hinders flame-retardant the extent to which something is delayed or held back