The Collaborative International Dictionary of English v.0.48:

Abruptly \Ab*rupt"ly\, adv.
   1. In an abrupt manner; without giving notice, or without the
      usual forms; suddenly.
      [1913 Webster]

   2. Precipitously.
      [1913 Webster] Abruptly pinnate

WordNet (r) 3.0 (2006):

abruptly
    adv 1: quickly and without warning; "he stopped suddenly" [syn:
           abruptly, suddenly, short, dead]

Moby Thesaurus II by Grady Ward, 1.0:

53 Moby Thesaurus words for "abruptly":
   a corps perdu, bang, bearishly, bluffly, bluntly, boorishly,
   brashly, brusquely, cavalierly, churlishly, crustily, curtly, dash,
   forthwith, gruffly, harshly, hastily, head over heels, headfirst,
   headforemost, headlong, heels over head, impetuously, impulsively,
   like a flash, like a thunderbolt, nastily, of a sudden,
   on short notice, plop, plump, plunk, pop, precipitantly,
   precipitately, precipitously, rashly, sharp, sharply, short,
   shortly, slap, slap-bang, smack, snippily, startlingly, sudden,
   suddenly, surprisingly, unawares, unexpectedly, without notice,
   without warning