The Collaborative International Dictionary of English v.0.48:

Calm \Calm\, v. i. [imp. & p. p. Calmed (k[aum]md); p. pr. &
   vb. n. Calming.] [Cf. F. calmer. See Calm, n.]
   1. To make calm; to render still or quiet, as elements; as,
      to calm the winds.
      [1913 Webster]

            To calm the tempest raised by Eolus.  --Dryden.
      [1913 Webster]

   2. To deliver from agitation or excitement; to still or
      soothe, as the mind or passions.
      [1913 Webster]

            Passions which seem somewhat calmed.  --Atterbury.

   Syn: To still; quiet; appease; allay; pacify; tranquilize;
        soothe; compose; assuage; check; restrain.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

calming \calming\ adj.
   1. tending to soothe or calm or tranquilize.

   Syn: ataractic, ataraxic, sedative, soothing, tranquilizing.
        [WordNet 1.5]

   2. freeing from fear and anxiety.

   Syn: assuasive, pacifying, soothing.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

calming
    n 1: the act of appeasing (as by acceding to the demands of)
         [syn: appeasement, calming]

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "calming":
   United Nations troops, abatement, allayment, alleviation,
   appeasement, appeasing, assuagement, blunting, conciliation,
   cradling, damping, deadening, demulsion, detente, diminution,
   dreamy, drowsy, dulcification, dulling, easing,
   easing of relations, falling-off, gentling, hushing, leniency,
   lessening, letdown, letup, lightening, loosening, lulling,
   mediation, mitigation, modulation, mollification, mollifying,
   pacification, pacifying, palliation, peace-keeping force,
   peacemaking, peacemongering, placability, placation, propitiation,
   quietening, quieting, reduction, relaxation, relaxation of tension,
   remission, restful, rocking, slackening, softening, soothful,
   soothing, stilling, subduement, tempering, tranquilization,
   tranquilizing