WordNet (r) 3.0 (2006):

double quick
    adv 1: at a faster speed; "now let's play the piece again
           double-quick" [syn: double time, double quick]

Moby Thesaurus II by Grady Ward, 1.0:

97 Moby Thesaurus words for "double quick":
   acceleration, agile, amain, apace, at flank speed, at the double,
   breakneck, crowded, dashing, double march, double time,
   double-quick time, double-time, eagle-winged, expeditious,
   expeditiously, express, fast, festination, fleet, flying,
   forced march, forwarding, galloping, goose step, hair-trigger,
   half step, hand over fist, hand over hand, hard-pressed,
   hard-pushed, hard-run, hastening, hastily, hasty, headlong,
   hell for leather, hell-bent, hell-bent for election, hurried,
   hurrying, hustling, in double time, in double-quick time, in high,
   in high gear, in seven-league boots, lickety-cut, lickety-split,
   light of heel, light-footed, lively, march, mercurial, nimble,
   nimble-footed, on the double, post, posthaste, precipitate,
   pressed, pressed for time, prompt, promptly, pushed, quick,
   quick as lightning, quick as thought, quick march, quick time,
   quickening, quickly, quickstep, quickstep march, rapid, rapidly,
   reckless, running, rushed, slow march, slow time, snappily, snappy,
   spanking, speedily, speeding, speedy, swift, swiftly, trippingly,
   under forced draft, whip and spur, winged, with all haste,
   with giant strides, with rapid strides, with speed