The Collaborative International Dictionary of English v.0.48:

R'egime \R['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.
      [1913 Webster]

            I dream . . . of the new r['e]gime which is to come.
                                                  --H. Kingsley.
      [1913 Webster]

   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.
      [1913 Webster]

   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.
      [1913 Webster]

WordNet (r) 3.0 (2006):

regime
    n 1: the organization that is the governing authority of a
         political unit; "the government reduced taxes"; "the matter
         was referred to higher authorities" [syn: government,
         authorities, regime]
    2: (medicine) a systematic plan for therapy (often including
       diet) [syn: regimen, regime]

Moby Thesaurus II by Grady Ward, 1.0:

59 Moby Thesaurus words for "regime":
   acid-ash diet, administration, allergy diet, bland diet,
   calorie chart, calorie counter, civil government,
   curative measures, cure, diabetic diet, diet, diet book, dietary,
   dietetics, dieting, direction, discipline, dispensation,
   disposition, empery, empire, first aid, form of government,
   governance, government, high-protein diet, high-vitamin diet,
   hospitalization, leadership, low-carbohydrate diet, low-salt diet,
   macrobiotic diet, management, medical treatment, medicamentation,
   medication, order, oversight, pap, political organization, polity,
   regime, regimen, regnancy, regulation, reign, rule, salt-free diet,
   soft diet, sovereignty, spoon victuals, supervision, sway, system,
   system of government, treatment, ulcer diet, vegetarianism,
   vitamin-deficiency diet