The Collaborative International Dictionary of English v.0.48:

Arrowhead \Ar"row*head`\ arrow-head \ar"row-head`\, n.
   1. the pointed head or striking tip of an arrow.
      [1913 Webster]

   2. (Bot.) An aquatic plant of the genus Sagittaria, esp.
      Sagittaria sagittifolia, -- named from the shape of the
      leaves.
      [1913 Webster]

WordNet (r) 3.0 (2006):

arrowhead
    n 1: the pointed head or striking tip of an arrow