The Collaborative International Dictionary of English v.0.48:

Ablative \Ab"la*tive\, a. [F. ablatif, ablative, L. ablativus
   fr. ablatus. See Ablation.]
   1. Taking away or removing. [Obs.]
      [1913 Webster]

            Where the heart is forestalled with misopinion,
            ablative directions are found needful to unteach
            error, ere we can learn truth.        --Bp. Hall.
      [1913 Webster]

   2. (Gram.) Applied to one of the cases of the noun in Latin
      and some other languages, -- the fundamental meaning of
      the case being removal, separation, or taking away.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ablative \Ab"la*tive\, (Gram.)
   The ablative case.
   [1913 Webster]

   ablative absolute, a construction in Latin, in which a noun
      in the ablative case has a participle (either expressed or
      implied), agreeing with it in gender, number, and case,
      both words forming a clause by themselves and being
      unconnected, grammatically, with the rest of the sentence;
      as, Tarquinio regnante, Pythagoras venit, i. e.,
      Tarquinius reigning, Pythagoras came.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ablative
    adj 1: relating to the ablative case
    2: tending to ablate; i.e. to be removed or vaporized at very
       high temperature; "ablative material on a rocket cone"
    n 1: the case indicating the agent in passive sentences or the
         instrument or manner or place of the action described by
         the verb [syn: ablative, ablative case]