Source : Webster's Revised Unabridged Dictionary (1913)

Charlock \Char"lock\, n. [AS. cerlic; the latter part perh. fr.
   AS. le['a]c leek. Cf. {Hemlock}.] (Bot.)
   A cruciferous plant ({Brassica sinapistrum}) with yellow
   flowers; wild mustard. It is troublesome in grain fields.
   Called also {chardock}, {chardlock}, {chedlock}, and
   {kedlock}.

   {Jointed charlock}, {White charlock}, a troublesome weed
      ({Raphanus Raphanistrum}) with straw-colored, whitish, or
      purplish flowers, and jointed pods: wild radish.

Source : WordNet®

charlock
     n : weedy Eurasian plant often a pest in grain fields [syn: {field
         mustard}, {wild mustard}, {chadlock}, {Brassica kaber}, {Sinapis
         arvensis}]