The Collaborative International Dictionary of English v.0.48:

Swoop \Swoop\, n.
   A falling on and seizing, as the prey of a rapacious bird;
   the act of swooping.
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         The eagle fell, . . . and carried away a whole litter
         of cubs at a swoop.                      --L'Estrange.
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The Collaborative International Dictionary of English v.0.48:

Swoop \Swoop\, v. t. [imp. & p. p. Swooped; p. pr. & vb. n.
   Swooping.] [OE. swopen, usually, to sweep, As. sw[=a]pan to
   sweep, to rush; akin to G. schweifen to rove, to ramble, to
   curve, OHG. sweifan to whirl, Icel. sveipa to sweep; also to
   AS. sw[imac]fan to move quickly. Cf. Sweep, Swift, a. &
   n., Swipe, Swivel.]
   1. To fall on at once and seize; to catch while on the wing;
      as, a hawk swoops a chicken.
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   2. To seize; to catch up; to take with a sweep.
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            And now at last you came to swoop it all. --Dryden.
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            The grazing ox which swoops it [the medicinal herb]
            in with the common grass.             --Glanvill.
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The Collaborative International Dictionary of English v.0.48:

Swoop \Swoop\, v. i.
   1. To descend with closed wings from a height upon prey, as a
      hawk; to stoop.
      [1913 Webster]

   2. To pass with pomp; to sweep. [Obs.] --Drayton.
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WordNet (r) 3.0 (2006):

swoop
    n 1: (music) rapid sliding up or down the musical scale; "the
         violinist was indulgent with his swoops and slides" [syn:
         swoop, slide]
    2: a very rapid raid
    3: a swift descent through the air
    v 1: move down on as if in an attack; "The raptor swooped down
         on its prey"; "The teacher swooped down upon the new
         students" [syn: pounce, swoop]
    2: move with a sweep, or in a swooping arc
    3: seize or catch with a swooping motion [syn: swoop, swoop
       up]