The Collaborative International Dictionary of English v.0.48:

Spasmodic \Spas*mod"ic\, n. (Med.)
   A medicine for spasm.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Spasmodic \Spas"mod"ic\, a. [Gr. ?; ? a convulsion + ? likeness:
   cf. F. spasmotique.]
   1. (Med.) Of or pertaining to spasm; consisting in spasm;
      occuring in, or characterized by, spasms; as, a spasmodic
      asthma.
      [1913 Webster]

   2. Soon relaxed or exhausted; convulsive; intermittent; as,
      spasmodic zeal or industry.
      [1913 Webster]

   Spasmodic croup (Med.), an affection of childhood
      characterized by a stoppage of brathing developed suddenly
      and without fever, and produced by spasmodic contraction
      of the vocal cords. It is sometimes fatal. Called also
      laryngismus stridulus, and childcrowing.

   Spasmodic stricture, a stricture caused by muscular spasm
      without structural change. See Organic stricture, under
      Organic.
      [1913 Webster]

WordNet (r) 3.0 (2006):

spasmodic
    adj 1: affected by involuntary jerky muscular contractions;
           resembling a spasm; "convulsive motions"; "his body made
           a spasmodic jerk"; "spastic movements" [syn:
           convulsive, spasmodic, spastic]
    2: occurring in spells and often abruptly; "fitful bursts of
       energy"; "spasmodic rifle fire" [syn: fitful, spasmodic]

Moby Thesaurus II by Grady Ward, 1.0:

239 Moby Thesaurus words for "spasmodic":
   acute, adrift, afflictive, afloat, agonizing, aimless, alternating,
   amorphous, arrhythmic, atrocious, biting, broken, broken off,
   capricious, careening, casual, cataclysmic, catchy, changeable,
   changeful, changing, chopped-off, choppy, convulsive, cramping,
   cruel, cyclical, decousu, desultory, deviable, deviating,
   deviative, deviatory, different, disarticulated, disastrous,
   disconnected, discontinued, discontinuous, discrete, disjunct,
   disjunctive, disordered, disorderly, dispersed, disproportionate,
   distressing, divaricate, divergent, diversified, diversiform,
   dizzy, eccentric, eclamptic, episodic, erose, erratic,
   excruciating, fast and loose, fickle, fidgety, fitful, flickering,
   flighty, flitting, fluctuating, formless, freakish, frivolous,
   giddy, gnawing, gratuitous, grave, griping, guttering, halting,
   haphazard, hard, harrowing, harsh, herky-jerky, heteroclite,
   hit-or-miss, hurtful, hurting, immethodical, impetuous, impulsive,
   inchoate, incoherent, inconsistent, inconstant, indecisive,
   indiscriminate, infirm, intermittent, intermitting, interrupted,
   irregular, irresolute, irresponsible, jagged, jerking, jerky,
   jiggety, jumpy, lurching, mazy, meaningless, mercurial, misshapen,
   moody, motley, mutable, nonconformist, noncontinuous, nonlinear,
   nonsequential, nonserial, nonstandard, nonsymmetrical,
   nonsystematic, nonuniform, occasional, orderless, orgasmic,
   painful, parenthetic, paroxysmal, patchy, periodic, piercing,
   planless, pluralistic, poignant, promiscuous, pulsating, pungent,
   racking, ragged, rambling, random, restless, rough, roving,
   saltatory, scatterbrained, scrappy, seismic, senseless, severe,
   shapeless, sharp, shifting, shifty, shooting, shuffling, snatchy,
   spasmatic, spasmic, spasmodical, spastic, spineless, sporadic,
   spotty, stabbing, staggering, stinging, straggling, straggly,
   sudden, suspended, systemless, tormenting, torturous, twitchety,
   twitching, twitchy, unaccountable, unarranged, uncertain,
   unclassified, unconnected, uncontrolled, undependable, undirected,
   undisciplined, unequable, unequal, uneven, unfixed, ungraded,
   unjoined, unmethodical, unmetrical, unordered, unorganized,
   unorthodox, unpredictable, unregular, unreliable, unrestrained,
   unrhythmical, unsettled, unsorted, unstable, unstable as water,
   unstaid, unsteadfast, unsteady, unsuccessive, unsustained,
   unsymmetrical, unsystematic, ununiform, upheaving, vacillating,
   vagrant, vague, variable, variegated, variform, various, varying,
   veering, vellicative, vicissitudinary, vicissitudinous, volatile,
   wandering, wanton, wavering, wavery, wavy, wayward, whimsical,
   wishy-washy, wobbling, wobbly