WARLOCK is a 7 letter word that starts with W.

1. \War"lock\, n. [OE. warloghe a deceiver, a name or the
   Devil, AS. w?rloga a belier or breaker of his agreement,
   word, or pledge; w?r covenant, troth (aki? to L. verus true;
   see {Very}) + loga a liar (in comp.), le['o]gan to lie. See
   3d {Lie}.]
   A male witch; a wizard; a sprite; an imp. [Written also
   {warluck}.] --Dryden.
   
         It was Eyvind Kallda's crew Of warlocks blue, With
         their caps of darkness hooded!           --Longfellow.
   
   

2. \War"lock\, a.
   Of or pertaining to a warlock or warlock; impish. [R.]
   
         Thou shalt win the warlock fight.        --J. R. Drak?.