Source : Webster's Revised Unabridged Dictionary (1913)

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.

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

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

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

Source : WordNet®

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