The Collaborative International Dictionary of English v.0.48:

Interference \In`ter*fer"ence\, n. [See Interfere.]
   [1913 Webster]
   1. The act or state of interfering; as, the stoppage of a
      machine by the interference of some of its parts; a
      meddlesome interference in the business of others.
      [1913 Webster]

   2. (Physics) The mutual influence, under certain conditions,
      as from streams of light, or pulsations of sound, or,
      generally, two waves or vibrations of any kind, producing
      certain characteristic phenomena, as colored fringes, dark
      bands, or darkness, in the case of light, silence or
      increased intensity in sounds; neutralization or
      superposition of waves generally.
      [1913 Webster]

   Note: The term is most commonly applied to light, and the
         undulatory theory of light affords the proper
         explanation of the phenomena which are considered to be
         produced by the superposition of waves, and are thus
         substantially identical in their origin with the
         phenomena of heat, sound, waves of water, and the like.
         [1913 Webster]

   3. (Patent Law) The act or state of interfering, or of
      claiming a right to the same invention.
      [1913 Webster]

   Interference figures (Optics), the figures observed when
      certain sections of crystallized bodies are viewed in
      converging polarized light; thus, a section of a uniaxial
      crystal, cut normal to the vertical axis, shows a series
      of concentric colored rings with a single black cross; --
      so called because produced by the interference of luminous
      waves.

   Interference fringe. (Optics) See Fringe.
      [1913 Webster]

WordNet (r) 3.0 (2006):

interference
    n 1: a policy of intervening in the affairs of other countries
         [syn: intervention, interference] [ant:
         noninterference, nonintervention]
    2: the act of hindering or obstructing or impeding [syn:
       hindrance, hinderance, interference]
    3: electrical or acoustic activity that can disturb
       communication [syn: noise, interference, disturbance]
    4: (American football) blocking a player's path with your body;
       "he ran interference for the quarterback"
    5: any obstruction that impedes or is burdensome [syn:
       hindrance, hinderance, hitch, preventive,
       preventative, encumbrance, incumbrance, interference]

Moby Thesaurus II by Grady Ward, 1.0:

157 Moby Thesaurus words for "interference":
   amplitude, antagonism, antinode, antipathy, arrest, arrestation,
   arrestment, atmospherics, backlash, blaring, blasting, blind spot,
   block, blockage, blocking, check, clashing, clogging, closing up,
   closure, collision, conflict, confutation, constriction,
   contradiction, contraposition, contrariety, counteraction,
   counterposition, counterworking, cramp, crankiness, crawling,
   creeping, crest, crotchetiness, de Broglie wave, delay, detainment,
   detention, difficulty, diffraction, dissent, drift,
   electromagnetic radiation, electromagnetic wave, encroachment,
   encumbrance, entrance, entrenchment, fade-out, fading, fixation,
   foot-dragging, frequency, frequency band, frequency spectrum,
   friction, frustration, guided wave, hampering, handicap, hindering,
   hindrance, hitch, holdback, holdup, impedance, impediment,
   impingement, imposition, in phase, incursion, infiltration, influx,
   infringement, inhibition, injection, inroad, insinuation,
   interceding, intercession, interjection, interloping,
   interposition, interposure, interruption, intervention, intruding,
   intrusion, invasion, irruption, kick, let, light,
   longitudinal wave, mechanical wave, meddling, negativism, node,
   noise, nonconformity, nuisance value, obstruction, obstructionism,
   obtrusion, occlusion, opposition, opposure, oppugnance, oppugnancy,
   out of phase, period, periodic wave, perverseness, radio wave, ray,
   reaction, recalcitrance, reception, recoil, reinforcement,
   renitency, repercussion, repression, repugnance, resistance,
   resonance, resonance frequency, restraint, restriction,
   retardation, retardment, revolt, seismic wave, setback, shock wave,
   snag, sound wave, squeeze, static, stranglehold, stricture,
   suppression, surface wave, swimming upstream, tidal wave,
   transverse wave, trespass, trespassing, trough, unlawful entry,
   wave, wave equation, wave motion, wave number, wavelength