Source : Webster's Revised Unabridged Dictionary (1913)

Spearhead \Spear"head`\, n.
   The pointed head, or end, of a spear.

Source : WordNet®

spearhead
     n 1: someone who leads or initiates an activity (attack or
          campaign etc.)
     2: the leading military unit in an attack
     3: the head and sharpened point of a spear [syn: {spearpoint},
        {spear-point}]

spearhead
     v : be the leader of; "She spearheded the effort to find a cure
         for the disease"