The Collaborative International Dictionary of English v.0.48:

Object \Ob"ject\ ([o^]b"j[e^]kt), n. [L. objectus. See Object,
   v. t.]
   1. That which is put, or which may be regarded as put, in the
      way of some of the senses; something visible or tangible
      and persists for an appreciable time; as, he observed an
      object in the distance; all the objects in sight; he
      touched a strange object in the dark.
      [1913 Webster]

   2. Anything which is set, or which may be regarded as set,
      before the mind so as to be apprehended or known; that of
      which the mind by any of its activities takes cognizance,
      whether a thing external in space or a conception formed
      by the mind itself; as, an object of knowledge, wonder,
      fear, thought, study, etc.
      [1913 Webster]

            Object is a term for that about which the knowing
            subject is conversant; what the schoolmen have
            styled the "materia circa quam."      --Sir. W.
                                                  Hamilton.
      [1913 Webster]

            The object of their bitterest hatred. --Macaulay.
      [1913 Webster]

   3. That toward which the mind, or any of its activities, is
      directed; that on which the purpose are fixed as the end
      of action or effort; that which is sought for; goal; end;
      aim; motive; final cause.
      [1913 Webster]

            Object, beside its proper signification, came to be
            abusively applied to denote motive, end, final cause
            . . . . This innovation was probably borrowed from
            the French.                           --Sir. W.
                                                  Hamilton.
      [1913 Webster]

            Let our object be, our country, our whole country,
            and nothing but our country.          --D. Webster.
      [1913 Webster]

   4. Sight; show; appearance; aspect. [Obs.] --Shak.
      [1913 Webster]

            He, advancing close
            Up to the lake, past all the rest, arose
            In glorious object.                   --Chapman.
      [1913 Webster]

   5. (Gram.) A word, phrase, or clause toward which an action
      is directed, or is considered to be directed; as, the
      object of a transitive verb.
      [1913 Webster]

   6. (Computers) Any set of data that is or can be manipulated
      or referenced by a computer program as a single entity; --
      the term may be used broadly, to include files, images
      (such as icons on the screen), or small data structures.
      More narrowly, anything defined as an object within an
      object-oriented programming language.
      [PJC]

   7. (Ontology) Anything which exists and which has attributes;
      distinguished from attributes, processes, and
      relations.
      [PJC]

   Object glass, the lens, or system of lenses, placed at the
      end of a telescope, microscope, etc., which is toward the
      object. Its function is to form an image of the object,
      which is then viewed by the eyepiece. Called also
      objective or objective lens. See Illust. of
      Microscope.

   Object lesson, a lesson in which object teaching is made
      use of.

   Object staff. (Leveling) Same as Leveling staff.

   Object teaching, a method of instruction, in which
      illustrative objects are employed, each new word or idea
      being accompanied by a representation of that which it
      signifies; -- used especially in the kindergarten, for
      young children.
      [1913 Webster]

WordNet (r) 3.0 (2006):

object lesson
    n 1: punishment intended as a warning to others; "they decided
         to make an example of him" [syn: example, deterrent
         example, lesson, object lesson]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "object lesson":
   admonishment, admonition, alarm, assignment, case, case in point,
   caution, caveat, chalk talk, demonstration, deterrent example,
   discourse, disquisition, emblem, example, exemplar,
   exemplification, exercise, explanation, exponent, exposition,
   final notice, final warning, harangue, hint, homework, homily,
   illustration, instance, instruction, lecture,
   lecture-demonstration, lesson, monition, moral, moral lesson,
   morality, moralization, notice, notification, preachment, recital,
   recitation, relevant instance, representative, sermon, set task,
   skull session, symbol, talk, task, teaching, threat, tip-off, type,
   typical example, ultimatum, verbum sapienti, warning,
   warning piece