The Collaborative International Dictionary of English v.0.48:

Sporadically \Spo*rad"ic*al*ly\, adv.
   In a sporadic manner.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sporadically
    adv 1: in a sporadic manner; "he only works sporadically" [syn:
           sporadically, periodically]

Moby Thesaurus II by Grady Ward, 1.0:

71 Moby Thesaurus words for "sporadically":
   at haphazard, at intervals, at irregular intervals, at large,
   at random, brokenly, by catches, by chance, by fits, by jerks,
   by snatches, capriciously, carelessly, chaotically, desultorily,
   diffusely, disconnectedly, discontinuously, dispersedly,
   eccentrically, erratically, every which way, everywhere, fitfully,
   haltingly, haphazardly, helter-skelter, here and there,
   higgledy-piggledy, hit or miss, impulsively, in all quarters,
   in places, in snatches, in spots, inconsistently, inconstantly,
   indiscriminately, infrequently, intermittently, irregularly,
   jerkily, lurchingly, nonuniformly, off and on, on occasion, passim,
   patchily, promiscuously, randomly, roughly, sloppily, sparsely,
   sparsim, spasmodically, spottily, throughout, uncertainly,
   uncommonly, unequally, unevenly, unmethodically, unpredictably,
   unrhythmically, unsteadily, unsystematically, ununiformly,
   variably, wherever you look, whimsically, wobblingly