At breakneck speed.

synonym: headlong.

Roget 684: with haste, with all haste, with breathless speed; in haste etc. adj.; apace etc. (swiftly) 274; amain^†; all at once etc. (instantaneously) 113; at short notice &c.; immediately etc. (early) 132; posthaste; by cable, by express, by telegraph, by forced marches.    hastily, precipitately etc. adj.; helter-skelter, hurry-skurry^†, holus-bolus; slapdash, slap-bang; full-tilt, full drive; heels over head, head and shoulders, headlong, a corps perdu [Fr.].    by fits and starts, by spurts; hop skip and jump.    ... show more

Roget 132: early, soon, anon, betimes, rath^†; eft, eftsoons; ere long, before long, shortly; beforehand; prematurely etc. adj.; precipitately etc. (hastily) 684; too soon; before its time, before one's time; in anticipation; unexpectedly etc. 508.    suddenly etc. (instantaneously) 113; before one can say 'Jack Robinson'," at short notice, extempore; on the spur of the moment, on the spur of the occasion [Bacon]; at once; on the spot, on the instant; at sight; offhand, out of hand; a' vue d'oeil [Fr.]; straight, straightway, straightforth^†; forthwith, incontinently, summarily, immediately, briefly, shortly, quickly, speedily, apace, before the ink is dry, almost immediately, presently at the first opportunity, in no long time, by and by, in a while, directly.    ... show more