The Collaborative International Dictionary of English v.0.48:

Tempestuous \Tem*pes"tu*ous\, a. [L. tempestuous: cf. OF.
   tempestueux, F. temp[^e]tueux.]
   Of or pertaining to a tempest; involving or resembling a
   tempest; turbulent; violent; stormy; as, tempestuous weather;
   a tempestuous night; a tempestuous debate. --
   Tem*pes"tu*ous*ly, adv. -- Tem*pes"tu*ous*ness, n.
   [1913 Webster]

         They saw the Hebrew leader,
         Waiting, and clutching his tempestuous beard.
                                                  --Longfellow.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tempestuousness
    n 1: a state of wild storminess
    2: a state of agitation or turbulent change or development; "the
       political ferment produced new leadership"; "social unrest"
       [syn: agitation, ferment, fermentation,
       tempestuousness, unrest]