The Collaborative International Dictionary of English v.0.48:

Oblanceolate \Ob*lan"ce*o*late\, a. [Pref. ob- + lanceolate.]
   Lanceolate in the reversed order, that is, narrowing toward
   the point of attachment more than toward the apex.
   [1913 Webster]

WordNet (r) 3.0 (2006):

oblanceolate
    adj 1: (of a leaf shape) having a broad rounded apex and a
           tapering base