The Collaborative International Dictionary of English v.0.48:

Incident \In"ci*dent\, n. [Cf. F. incident.]
   1. That which falls out or takes place; an event; casualty;
      occurrence.
      [1913 Webster]

   2. That which happens aside from the main design; an
      accidental or subordinate action or event.
      [1913 Webster]

            No person, no incident, in a play but must be of use
            to carry on the main design.          --Dryden.
      [1913 Webster]

   3. (Law) Something appertaining to, passing with, or
      depending on, another, called the principal. --Tomlins.

   Syn: Circumstance; event; fact; adventure; contingency;
        chance; accident; casualty. See Event.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Incident \In"ci*dent\, a. [L. incidens, -entis, p. pr. & of
   incidere to fall into or upon; pref. in- in, on + cadere to
   fall: cf. F. incident. See Cadence.]
   [1913 Webster]
   1. Falling or striking upon, as a ray of light upon a
      reflecting surface.
      [1913 Webster]

   2. Coming or happening accidentally; not in the usual course
      of things; not in connection with the main design; not
      according to expectation; casual; fortuitous.
      [1913 Webster]

            As the ordinary course of common affairs is disposed
            of by general laws, so likewise men's rarer incident
            necessities and utilities should be with special
            equity considered.                    --Hooker.
      [1913 Webster]

   3. Liable to happen; apt to occur; befalling; hence,
      naturally happening or appertaining.
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            All chances incident to man's frail life. --Milton.
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            The studies incident to his profession. --Milward.
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   4. (Law) Dependent upon, or appertaining to, another thing,
      called the principal.
      [1913 Webster]

   Incident proposition (Logic), a proposition subordinate to
      another, and introduced by who, which, whose, whom, etc.;
      as, Julius, whose surname was C[ae]sar, overcame Pompey.
      --I. Watts.
      [1913 Webster]

WordNet (r) 3.0 (2006):

incident
    adj 1: falling or striking of light rays on something; "incident
           light"
    2: (sometimes followed by `to') minor or casual or subordinate
       in significance or nature or occurring as a chance
       concomitant or consequence; "incidental expenses"; "the road
       will bring other incidental advantages"; "extra duties
       incidental to the job"; "labor problems incidental to a rapid
       expansion"; "confusion incidental to a quick change" [syn:
       incidental, incident] [ant: basic]
    n 1: a single distinct event
    2: a public disturbance; "the police investigated an incident at
       the bus station"

Moby Thesaurus II by Grady Ward, 1.0:

77 Moby Thesaurus words for "incident":
   action, adventure, affair, anagnorisis, angle, architectonics,
   architecture, argument, atmosphere, background, catastrophe,
   characterization, circumstance, color, commotion, complication,
   condition, conjuncture, contingency, continuity, contrivance,
   denouement, design, development, device, disturbance, do, episode,
   event, eventuality, experience, fable, fact, falling action,
   fracas, gimmick, hap, happening, happenstance, juncture, line,
   local color, matter of fact, mood, motif, movement, mythos,
   occasion, occurrence, particular, peripeteia, phenomenon, plan,
   plot, proceeding, reality, recognition, rising action, scene,
   scheme, secondary plot, set-to, skirmish, slant, story, structure,
   subject, subplot, switch, thematic development, theme, to-do, tone,
   topic, turn of events, twist, upset



Bouvier's Law Dictionary, Revised 6th Ed (1856):

INCIDENT. A thing depending upon, appertaining to, or following another,
called the principal.
     2. The power of punishing for contempt is incident to a court of
record; rent is incident to a reversion; distress to rent; estovers of woods
to a tenancy for a life or years. 1 Inst. 151; Noy's Max. n. 13; Vin. Ab.
h.. t.; Dane's Ab. h.t.; Com. Dig. h.t., and the references there; Bro.
Ab. h.t.; Roll's Ab. 75.