The Collaborative International Dictionary of English v.0.48:

Bullate \Bul"late\ (b[u^]l"l[asl]t/), a. [L. bullatus, fr. bulla
   bubble.] (Biol.)
   Appearing as if blistered; inflated; puckered.
   [1913 Webster]

   Bullate leaf (Bot.), a leaf, the membranous part of which
      rises between the veins puckered elevations convex on one
      side and concave on the other.
      [1913 Webster]

WordNet (r) 3.0 (2006):

bullate
    adj 1: of leaves; appearing puckered as if blistered