The Collaborative International Dictionary of English v.0.48:

Swiftly \Swift"ly\, adv.
   In a swift manner; with quick motion or velocity; fleetly.
   --Wyclif.
   [1913 Webster]

WordNet (r) 3.0 (2006):

swiftly
    adv 1: in a swift manner; "she moved swiftly" [syn: swiftly,
           fleetly]

Moby Thesaurus II by Grady Ward, 1.0:

99 Moby Thesaurus words for "swiftly":
   PDQ, abruptly, agilely, amain, apace, at flank speed, at once,
   briefly, briskly, by forced marches, cursorily, decisively,
   directly, double-quick, expeditiously, fast, feverishly, flat-out,
   fleetingly, flickeringly, flittingly, for a moment, forthwith,
   full tilt, furiously, hand over fist, hand over hand, hastily,
   hell for leather, hell-bent, hell-bent for election,
   helter-skelter, hotfoot, hurriedly, hurry-scurry, immediately,
   in a flash, in a jiffy, in a trice, in an instant, in double time,
   in double-quick time, in high, in high gear, in no time,
   in passing, in seven-league boots, instanter, instantly,
   lickety-cut, lickety-split, like a shot, like greased lightning,
   momentarily, nimbly, on the double, on the instant, on the run,
   on the spot, pell-mell, post, posthaste, precipitately,
   pretty damned quick, promptly, pronto, quick, quickly, rapidly,
   readily, right away, right off, shortly, slapdash, smartly,
   snappily, speedily, spryly, straightaway, straightway, subito,
   suddenly, summarily, superficially, transiently, trippingly,
   under forced draft, unexpectedly, whip and spur, with a rush,
   with all haste, with all speed, with dispatch, with giant strides,
   with haste, with rapid strides, with speed, without delay,
   without further delay