1. Mode or system of rule or management; character of government, or of the prevailing social system. I dream . . . Of the new regime which is to come. (H. Kingsley)
2. (Science: physics) The condition of a river with respect to the rate of its flow, as measured by the volume of water passing different cross-sections in a given time, uniform regime being the condition when the flow is equal and uniform at all the cross sections. The ancient regime, or Ancien regime F, the former political and social system, as distinguished from the modern; especially, the political and social system existing in France before the revolution of 1789.