R\'egimeR['e]`gime"\ (r?`zh?m"), n. [F. See Regimen.]1. Mode or system of rule or management; character of government, or of the prevailing social system. I dream . . . of the new r['e]gime which is to come. --H. Kingsley. 2. (Hydraul.) 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 r['e]gime being the condition when the flow is equal and uniform at all the cross sections. The ancient r['e]gime, or Ancien r['e]gime [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.