The Collaborative International Dictionary of English v.0.48:

Flying \Fly"ing\, a. [From Fly, v. i.]
   Moving in the air with, or as with, wings; moving lightly or
   rapidly; intended for rapid movement.
   [1913 Webster]

   Flying army (Mil.) a body of cavalry and infantry, kept in
      motion, to cover its own garrisons and to keep the enemy
      in continual alarm. --Farrow.

   Flying artillery (Mil.), artillery trained to rapid
      evolutions, -- the men being either mounted or trained to
      spring upon the guns and caissons when they change
      position.

   Flying bridge, Flying camp. See under Bridge, and
      Camp.

   Flying buttress (Arch.), a contrivance for taking up the
      thrust of a roof or vault which can not be supported by
      ordinary buttresses. It consists of a straight bar of
      masonry, usually sloping, carried on an arch, and a solid
      pier or buttress sufficient to receive the thrust. The
      word is generally applied only to the straight bar with
      supporting arch.

   Flying colors, flags unfurled and waving in the air; hence:

   To come off with flying colors, to be victorious; to
      succeed thoroughly in an undertaking.

   Flying doe (Zool.), a young female kangaroo.

   Flying dragon.
   (a) (Zool.) See Dragon, 6.
   (b) A meteor. See under Dragon.

   Flying Dutchman.
   (a) A fabled Dutch mariner condemned for his crimes to sail
       the seas till the day of judgment.
   (b) A spectral ship.

   Flying fish. (Zool.) See Flying fish, in the Vocabulary.


   Flying fox (Zool.), see Flying fox in the vocabulary.

   Flying frog (Zool.), either of two East Indian tree frogs
      of the genus Rhacophorus (Rhacophorus nigrapalmatus
      and Rhacophorus pardalis), having very large and broadly
      webbed feet, which serve as parachutes, and enable it to
      make very long leaps.

   Flying gurnard (Zool.), a species of gurnard of the genus
      Cephalacanthus or Dactylopterus, with very large
      pectoral fins, said to be able to fly like the flying
      fish, but not for so great a distance.

   Note: Three species are known; that of the Atlantic is
         Cephalacanthus volitans.

   Flying jib (Naut.), a sail extended outside of the standing
      jib, on the flying-jib boom.

   Flying-jib boom (Naut.), an extension of the jib boom.

   Flying kites (Naut.), light sails carried only in fine
      weather.

   Flying lemur. (Zool.) See Colugo.

   Flying level (Civil Engin.), a reconnoissance level over
      the course of a projected road, canal, etc.

   Flying lizard. (Zool.) See Dragon, n. 6.

   Flying machine, any apparatus for navigating through the
      air, especially a heavier-than-air machine. -- Flying
   mouse (Zool.), the opossum mouse (Acrobates pygm[ae]us), a
      marsupial of Australia. Called also feathertail glider.

   Note: It has lateral folds of skin, like the flying
         squirrels, and a featherlike tail. -- Flying party
      (Mil.), a body of soldiers detailed to hover about an
      enemy. -- Flying phalanger (Zool.), one of several
      species of small marsuupials of the genera Petaurus and
      Belideus, of Australia and New Guinea, having lateral
      folds like those of the flying squirrels. The sugar
      squirrel (Belideus sciureus), and the ariel (Belideus
      ariel), are the best known; -- called also squirrel
      petaurus and flying squirrel. See Sugar squirrel. --
   Flying pinion, the fly of a clock. -- Flying sap (Mil.),
      the rapid construction of trenches (when the enemy's fire
      of case shot precludes the method of simple trenching), by
      means of gabions placed in juxtaposition and filled with
      earth. -- Flying shot, a shot fired at a moving object,
      as a bird on the wing. -- Flying spider. (Zool.) See
      Ballooning spider. -- Flying squid (Zool.), an oceanic
      squid (Ommastrephes Bartramii syn. Sthenoteuthis
      Bartramii), abundant in the Gulf Stream, which is able to
      leap out of the water with such force that it often falls
      on the deck of a vessel. -- Flying squirrel (Zool.) See
      Flying squirrel, in the Vocabulary. -- Flying start, a
      start in a sailing race in which the signal is given while
      the vessels are under way. -- Flying torch (Mil.), a
      torch attached to a long staff and used for signaling at
      night.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

arc-boutant \arc`-bou`tant"\ ([aum]r`b[=oo]`t[aum]N), n. [F.]
   (Arch.)
   A buttress that stands apart from the main structure and
   connected to it by an arch; same as flying buttress.
   --Gwilt.

   Syn: flying buttress
        [1913 Webster + WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Buttress \But"tress\, n. [OE. butrasse, boterace, fr. F. bouter
   to push; cf. OF. bouteret (nom. sing. and acc. pl. bouterez)
   buttress. See Butt an end, and cf. Butteris.]
   1. (Arch.) A projecting mass of masonry, used for resisting
      the thrust of an arch, or for ornament and symmetry.
      [1913 Webster]

   Note: When an external projection is used merely to stiffen a
         wall, it is a pier.
         [1913 Webster]

   2. Anything which supports or strengthens. "The ground pillar
      and buttress of the good old cause of nonconformity."
      --South.
      [1913 Webster]

   Flying buttress. See Flying buttress.
      [1913 Webster]

WordNet (r) 3.0 (2006):

flying buttress
    n 1: a buttress that stands apart from the main structure and
         connected to it by an arch [syn: flying buttress, arc-
         boutant]