Retrorse

from WordNet (r) 3.0 (2006)

retrorse
    adj 1: bent or curved backward or downward; "leaves with
           retrorse barbs" [ant: {antrorse}]

from The Collaborative International Dictionary of English v.0.48

Retrorse \Re*trorse"\, a. [L. retrorsus, retroversus; retro back
   + vertere, versum, to turn. Cf. {Retrovert}.]
   Bent backward or downward. -- {Re*trorse"ly}, adv.
   [1913 Webster]