spear·head /-ˌhɛd/
  矛尖,突擊隊的先遣隊,攻擊的最前線(vt.)做先鋒,在前面帶頭做先鋒
  Spear·head n. The pointed head, or end, of a spear.
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  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]
       v : be the leader of; "She spearheded the effort to find a cure
           for the disease"