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.

Roil \Roil\, v. i.
   1. To wander; to roam. [Obs.]

   2. To romp. [Prov. Eng.] --Halliwell.

Source : WordNet®

roil
     v 1: be agitated; "the sea was churning in the storm" [syn: {churn},
           {boil}, {moil}]
     2: make turbid by stirring up the sediments of [syn: {rile}]