The Collaborative International Dictionary of English v.0.48:

flyover \flyover\ n.
   1. the upper level of a crossing of two highways at different
      levels; called in the United States an overpass; as, an
      overpass is called a flyover or a flypast in England.
      [Brit.]

   Syn: overpass, flypast.
        [WordNet 1.5]

   2. a low-altitude flight (usually of military aircraft) over
      spectators on the ground.

   Syn: flypast.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

flypast \fly"past\ (fl[imac]"p[a^]st), n.
   1. the upper level of a crossing of two highways at different
      levels; same as flyover; called in the United States an
      overpass. [Brit.]

   Syn: overpass, flyover.
        [WordNet 1.5]

   2. a low-altitude flight (usually of military aircraft) over
      spectators on the ground.

   Syn: flyover.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Overpass \O`ver*pass"\, v. i.
   To pass over, away, or off.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

overpass \o"ver*pass`\, n.
   A road or other pathway which passes over another road,
   railroad, or other path; as, he stopped on the street under
   the railroad overpass.
   [PJC]

The Collaborative International Dictionary of English v.0.48:

Overpass \O`ver*pass"\, v. t. [imp. & p. p. Overpassed; p. pr.
   & vb. n. Overpassing.] [Cf. Surpass.]
   [1913 Webster]
   1. To go over or beyond; to cross; as, to overpass a river;
      to overpass limits.
      [1913 Webster]

   2. To pass above; -- of roadways and other paths; as, the
      highway overpasses the railroad tracks.
      [PJC]

   3. To pass over; to omit; to overlook; to disregard.
      [1913 Webster]

            All the beauties of the East
            He slightly viewed and slightly overpassed.
                                                  --Milton.
      [1913 Webster]

   4. To surpass; to excel. [R.] --R. Browning.
      [1913 Webster]

WordNet (r) 3.0 (2006):

overpass
    n 1: bridge formed by the upper level of a crossing of two
         highways at different levels [syn: overpass, flyover]

Moby Thesaurus II by Grady Ward, 1.0:

160 Moby Thesaurus words for "overpass":
   Bifrost, access, aisle, alley, ambulatory, aperture, arcade,
   artery, avenue, bascule bridge, bateau bridge, best, better,
   blink at, bridge, cantilever bridge, cap, carrefour, catwalk,
   channel, cloister, cloverleaf, colonnade, communication, conduit,
   connection, corridor, course, cover, covered way, crossing,
   crosspoint, crossroad, crosswalk, crossway, defile, discount,
   disregard, distance, do, drawbridge, exaggerate, exaggeration,
   exceed, excel, excess, exit, fail, ferry, floating bridge, flyover,
   footbridge, ford, forget, gallery, gangboard, gangplank, gangway,
   get ahead of, go beyond, go one better, go over, grade crossing,
   hold the field, ignore, improve on, inlet, interchange,
   intercrossing, intersection, inundation, junction, lane,
   leave behind, level crossing, lift bridge, measure, omit, opening,
   outdistance, outlet, outweigh, overbalance, overbear, overbridge,
   overcome, overcrossing, overdo, overflowing, overgo, overgrowth,
   overjump, overleap, overlook, overreach, overrun, overrunning,
   overshoot, overshoot the field, overshoot the mark, overspreading,
   overstep, overstride, overtop, pass, pass over, pass through,
   passage, passageway, patrol, perambulate, peregrinate, pererrate,
   perfect, ply, pontoon bridge, portico, predominate, preponderate,
   prevail, railroad tunnel, range, range over, reconnoiter,
   rope bridge, rotary, scour, scour the country, scout,
   shoot ahead of, span, steal a march, stepping-stone, stepstone,
   superabound, superiority, surpass, surplus, suspension bridge,
   sweep, swing bridge, toll bridge, top, tower above, tower over,
   track, traffic circle, traject, trajet, transcend, transit,
   travel over, travel through, traverse, trump, tunnel,
   undercrossing, underpass, viaduct, voyage