The Collaborative International Dictionary of English v.0.48:

Sagittate \Sag"it*tate\, a. [NL. sagittatus, fr. L. sagitta an
   arrow.]
   Shaped like an arrowhead; triangular, with the two basal
   angles prolonged downward.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sagittate
    adj 1: (of a leaf shape) like an arrow head without flaring base
           lobes [syn: sagittate, sagittiform, arrow-shaped]