The Collaborative International Dictionary of English v.0.48:

aeroplane \aer"*o*plane`\ aeroplane \a"["e]r*o*plane`\, n.
   [a["e]ro- + plane.] (A["e]ronautics)
   1. A light rigid plane used in a["e]rial navigation to oppose
      sudden upward or downward movement in the air, as in
      gliding machines; specif., such a plane slightly inclined
      and driven forward as a lifting device in some flying
      machines. Also called airfoil.
      [Webster 1913 Suppl.]

   2. Hence: A heavier-than-air flying machine using such a
      device to provide lift; an airplane. In a modern
      aeroplane, the airfoils are called the wings, and most
      of the lift is derived from these surfaces. In contrast to
      helicopters, the wings are fixed to the passenger
      compartment (airframe) and do not move relative to the
      frame; thus such a machine is called a fixed-wing
      aircraft. These machines are called monoplanes, biplanes,
      triplanes, or quadruplanes, according to the number of
      main supporting planes (wings) used in their construction.
      After 1940 few planes with more than one airfoil were
      constructed, and these are used by hobbyists or for
      special purposes. Being heavier than air they depend for
      their levitation on motion imparted by the thrust from
      either propellers driven by an engine, or, in a jet plane,
      by the reaction from a high-velocity stream of gases
      expelled rearward from a jet engine. They start from the
      ground by a run on small wheels or runners, and are guided
      by a steering apparatus consisting of horizontal and
      vertical movable planes, which usually form part of the
      wings or tail. There are many varieties of form and
      construction, which in some cases are known by the names
      of their inventors. In U.S., an aeroplane is usually
      called an airplane or plane.
      [Webster 1913 Suppl. +PJC]

The Collaborative International Dictionary of English v.0.48:

airplane \air"plane\ n.
   a heavier-than-air aircraft. Same as aeroplane[2].
   [PJC]

WordNet (r) 3.0 (2006):

airplane
    n 1: an aircraft that has a fixed wing and is powered by
         propellers or jets; "the flight was delayed due to trouble
         with the airplane" [syn: airplane, aeroplane, plane]

Moby Thesaurus II by Grady Ward, 1.0:

216 Moby Thesaurus words for "airplane":
   Cub, VTOL, adjustable propeller, aeroplane, afterburner, aileron,
   air ambulance, air controls, air scoop, air scout, aircraft,
   airfreighter, airlift, airliner, airscrew, all-weather fighter,
   ambulance, amphibian transport, antisubmarine plane,
   assault transport, astrodome, attack bomber, avion, avion-canon,
   balloon, bay, be airborne, beaching gear, biplane, blister, body,
   bomb bay, bomber, bonnet, bow, brace wire, bubble, bubble canopy,
   bubble hood, bucket seat, cabin, canard, canopy, cargo plane,
   cargo transport, cat strip, chassis, chin, club plane,
   coaxial propellers, cockpit, coke-bottle fuselage, control surface,
   control wires, convertiplane, cowl, crew compartment, crop-duster,
   cruise, cruiser, deck, dihedral, dive bomber, dorsal airdome,
   drift, drone, dual controls, ejection seat, ejector, elevator,
   elevon, escort fighter, ferry, fighter, fin, finger patch, flap,
   flit, float, fly, flying banana, flying fortress, flying machine,
   flying platform, freight transport, freighter, fuel injector,
   fuselage, gas-shaft hood, glide, glider, gore, grasshopper,
   ground-attack fighter, gull wing, gun mount, hatch,
   heavier-than-air craft, heavy bomber, heavy transport, helicopter,
   hood, hop, hover, hovercraft, hunter, hydroplane, instruments,
   interceptor, jackstay, jet, jet bomber, jet pipe, jet plane, keel,
   killer, kite, laminar-flow system, landing gear, launching gear,
   launching tube, leading edge, light bomber, light transport, liner,
   long-range bomber, longeron, mailplane, medium bomber,
   military transport, mobile command post, monoplace, monoplane,
   mosquito, multipurpose plane, nacelle, naval aircraft,
   naval bomber, navigate, night fighter, nose, observation plane,
   ornithopter, pants, parasol, parasol wing, pathfinder,
   patrol bomber, patrol plane, picket patrol plane,
   pilotless aircraft, plane, pod, pontoon, precision bomber,
   private plane, prop, propeller, propeller plane,
   radar picket plane, reconnaissance plane, rescue helicopter,
   robot plane, rotor plane, rudder, rudder bar, sail, sailplane,
   scout, scout plane, seaplane, sesquiplane, ship, ski landing gear,
   ski-plane, sky truck, slitwing, soar, spinner, spoiler,
   sport plane, spotter plane, spray strip, spy plane, stabilizator,
   stabilizer, stay, stick, stick control, stratofreighter, stratojet,
   stressed skin, strut, tail, tail plane, tail skid, take the air,
   take wing, tandem plane, torpedo bomber, torpedo strike aircraft,
   trainer, trainer-bomber, trainer-fighter, transport, triplane,
   troop carrier, troop transport, truss, turbojet, turret,
   undercarriage, volplane, wheel parts, wing, wing radiator