The Collaborative International Dictionary of English v.0.48:

Spasmodical \Spas*mod"ic*al\, a.
   Same as Spasmodic, a. -- Spas*mod"ic*al*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

spasmodically
    adv 1: with spasms; "the mouth was slightly open, and jerked
           violently and spasmodically at one corner" [syn:
           spasmodically, jerkily]
    2: in spurts and fits; "I began to write intermittently and
       spasmodically"

Moby Thesaurus II by Grady Ward, 1.0:

66 Moby Thesaurus words for "spasmodically":
   at haphazard, at intervals, at irregular intervals, at random,
   brokenly, by catches, by chance, by fits, by jerks, by snatches,
   capriciously, carelessly, chaotically, desultorily, disconnectedly,
   discontinuously, eccentrically, erratically, every which way,
   fitfully, flutteringly, haltingly, haphazardly, helter-skelter,
   higgledy-piggledy, hit or miss, impulsively, in snatches, in spots,
   inconsistently, inconstantly, indiscriminately, intermittently,
   irregularly, jerkily, lurchingly, nonuniformly, off and on,
   patchily, promiscuously, quakingly, quaveringly, quiveringly,
   randomly, roughly, saltatorily, shakily, shudderingly, sloppily,
   sporadically, spottily, tremblingly, tremulously, uncertainly,
   unequally, unevenly, unmethodically, unpredictably, unrhythmically,
   unsteadily, unsystematically, ununiformly, variably, waveringly,
   whimsically, wobblingly