The Collaborative International Dictionary of English v.0.48:

Churning \Churn"ing\, n.
   1. The act of one who churns.
      [1913 Webster]

   2. The quantity of butter made at one operation.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Churn \Churn\, v. t. [imp. & p. p. Churned (ch[^u]rnd); p. pr.
   & vb. n. Churning.] [OE. chernen, AS. cernan; akin to LG.
   karnen, G. kernen, D. karnen, Dan. kierne, Sw. k[aum]rna, and
   also to E. corn, kernel, the meaning coming from the idea of
   extracting the kernel or marrow. See Kernel.]
   1. To stir, beat, or agitate, as milk or cream in a churn, in
      order to make butter.
      [1913 Webster]

   2. To shake or agitate with violence.
      [1913 Webster]

            Churned in his teeth, the foamy venom rose.
                                                  --Addison.
      [1913 Webster]

WordNet (r) 3.0 (2006):

churning
    adj 1: moving with or producing or produced by vigorous
           agitation; "winds whipped the piled leaves into churning
           masses"; "a car stuck in the churned-up mud" [syn:
           churning, churned-up]
    2: (of a liquid) agitated vigorously; in a state of turbulence;
       "the river's roiling current"; "turbulent rapids" [syn:
       churning, roiling, roiled, roily, turbulent]