The Collaborative International Dictionary of English v.0.48:

Behavior \Be*hav"ior\, n.
   Manner of behaving, whether good or bad; mode of conducting
   one's self; conduct; deportment; carriage; -- used also of
   inanimate objects; as, the behavior of a ship in a storm; the
   behavior of the magnetic needle.
   [1913 Webster]

         A gentleman that is very singular in his behavior.
                                                  --Steele.
   [1913 Webster]

   To be upon one's good behavior, To be put upon one's good
   behavior, to be in a state of trial, in which something
      important depends on propriety of conduct.

   During good behavior, while (or so long as) one conducts
      one's self with integrity and fidelity or with propriety.
      [1913 Webster]

   Syn: Bearing; demeanor; manner.

   Usage: Behavior, Conduct. Behavior is the mode in which
          we have or bear ourselves in the presence of others or
          toward them; conduct is the mode of our carrying
          ourselves forward in the concerns of life. Behavior
          respects our manner of acting in particular cases;
          conduct refers to the general tenor of our actions. We
          may say of soldiers, that their conduct had been
          praiseworthy during the whole campaign, and their
          behavior admirable in every instance when they met the
          enemy.
          [1913 Webster]

WordNet (r) 3.0 (2006):

behavior
    n 1: manner of acting or controlling yourself [syn: behavior,
         behaviour, conduct, doings]
    2: the action or reaction of something (as a machine or
       substance) under specified circumstances; "the behavior of
       small particles can be studied in experiments" [syn:
       behavior, behaviour]
    3: (behavioral attributes) the way a person behaves toward other
       people [syn: demeanor, demeanour, behavior,
       behaviour, conduct, deportment]
    4: (psychology) the aggregate of the responses or reactions or
       movements made by an organism in any situation [syn:
       behavior, behaviour]

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "behavior":
   Pavlovian conditioning, act, acting, action, actions, activism,
   activity, bearing, comportment, conditioned response, conditioning,
   conduct, demeanor, deportment, doing, employment, exercise,
   function, functioning, instrumental conditioning, manner, manners,
   mien, movements, negative reinforcement, occupation,
   operant conditioning, operation, operations, play,
   positive reinforcement, practice, praxis, psychagogy, reeducation,
   reflex, reinforcement, reorientation, swing, unconditioned reflex,
   way, work, working, workings



The Devil's Dictionary (1881-1906):

BEHAVIOR, n.  Conduct, as determined, not by principle, but by
breeding.  The word seems to be somewhat loosely used in Dr. Jamrach
Holobom's translation of the following lines from the _Dies Irae_:

        Recordare, Jesu pie,
        Quod sum causa tuae viae.
        Ne me perdas illa die.

    Pray remember, sacred Savior,
    Whose the thoughtless hand that gave your
    Death-blow.  Pardon such behavior.