Source : Webster's Revised Unabridged Dictionary (1913)

Vehement \Ve"he*ment\, a. [L. vehemens, the first part of which
   is perhaps akin to vehere to carry, and the second mens mind:
   cf. F. v['e]h['e]ment. Cf. {Vehicle}, and {Mental}.]
   1. Acting with great force; furious; violent; impetuous;
      forcible; mighty; as, vehement wind; a vehement torrent; a
      vehement fire or heat.

   2. Very ardent; very eager or urgent; very fervent;
      passionate; as, a vehement affection or passion.
      ``Vehement instigation.'' --Shak. ``Vehement desire.''
      --Milton.

   Syn: Furious; violent; raging; impetuous; passionate; ardent;
        eager; hot; fervid; burning.

Source : WordNet®

vehement
     adj 1: marked by extreme intensity of emotions or convictions;
            inclined to react violently; fervid; "fierce loyalty";
            "in a tearing rage"; "vehement dislike"; "violent
            passions" [syn: {fierce}, {tearing}, {violent}, {trigger-happy}]
     2: characterized by great force or energy; "vehement deluges of
        rain"; "vehement clapping"; "a vehement defense"