The Collaborative International Dictionary of English v.0.48:

Actor \Ac"tor\, n. [L. actor, fr. agere to act.]
   1. One who acts, or takes part in any affair; a doer.
      [1913 Webster]

   2. A theatrical performer; a stageplayer.
      [1913 Webster]

            After a well graced actor leaves the stage. --Shak.
      [1913 Webster]

   3. (Law)
      (a) An advocate or proctor in civil courts or causes.
          --Jacobs.
      (b) One who institutes a suit; plaintiff or complainant.
          [1913 Webster]

WordNet (r) 3.0 (2006):

actor
    n 1: a theatrical performer [syn: actor, histrion, player,
         thespian, role player]
    2: a person who acts and gets things done; "he's a principal
       actor in this affair"; "when you want something done get a
       doer"; "he's a miracle worker" [syn: actor, doer,
       worker]

The Free On-line Dictionary of Computing (19 January 2023):

Actor

    An object-oriented language for Microsoft
   Windows written by Charles Duff of the Whitewater Group ca.
   1986.  It has Pascal/C-like syntax.  Uses a
   token-threaded interpreter.  Early binding is an option.

   ["Actor Does More than Windows", E.R. Tello, Dr Dobb's J
   13(1):114-125 (Jan 1988)].

   (1994-11-08)


The Free On-line Dictionary of Computing (19 January 2023):

actor

   1.  In object-oriented programming, an object
   which exists as a concurrent process.

   2.  In Chorus, the unit of resource
   allocation.

   (1994-11-08)