The Collaborative International Dictionary of English v.0.48:

Roil \Roil\, v. t. [imp. & p. p. Roiled; p. pr. & vb. n.
   Roiling.] [Cf. OE. roilen to wander; possibly fr. OF.
   roeler to roll, equiv. to F. rouler. See Roll, v., and cf.
   Rile.]
   1. To render turbid by stirring up the dregs or sediment of;
      as, to roil wine, cider, etc., in casks or bottles; to
      roil a spring.
      [1913 Webster]

   2. To disturb, as the temper; to ruffle the temper of; to
      rouse the passion of resentment in; to perplex.
      [1913 Webster]

            That his friends should believe it, was what roiled
            him [Judge Jeffreys] exceedingly.     --R. North.
      [1913 Webster]

   Note: Provincial in England and colloquial in the United
         States. A commoner, but less approved, form is rile.
         [1913 Webster]

WordNet (r) 3.0 (2006):

roiling
    adj 1: (of a liquid) agitated vigorously; in a state of
           turbulence; "the river's roiling current"; "turbulent
           rapids" [syn: churning, roiling, roiled, roily,
           turbulent]