The Collaborative International Dictionary of English v.0.48:

Spastic \Spas"tic\, a. [L. spasticus, Gr. ?, fr. ? to draw: cf.
   F. spastique. See Spasm.] (Med.)
   Of or pertaining to spasm; spasmodic; especially, pertaining
   to tonic spasm; tetanic.
   [1913 Webster]

WordNet (r) 3.0 (2006):

spastic
    adj 1: relating to or characterized by spasm; "a spastic colon";
           "spastic paralysis is a spastic form of cerebral palsy"
    2: suffering from spastic paralysis; "a spastic child"
    3: affected by involuntary jerky muscular contractions;
       resembling a spasm; "convulsive motions"; "his body made a
       spasmodic jerk"; "spastic movements" [syn: convulsive,
       spasmodic, spastic]
    n 1: a person suffering from spastic paralysis

Moby Thesaurus II by Grady Ward, 1.0:

88 Moby Thesaurus words for "spastic":
   apoplectic, arthritic, broken, capricious, careening, case,
   cataclysmic, catchy, choppy, consumptive, convulsive, desultory,
   deviative, disastrous, disconnected, discontinuous, dyspeptic,
   eccentric, eclamptic, epileptic, erratic, fidgety, fitful,
   flickering, fluctuating, guttering, halting, herky-jerky,
   heteroclite, immethodical, inconstant, incurable, inpatient,
   intermittent, intermitting, invalid, irregular, jerking, jerky,
   jiggety, jumpy, lurching, nonuniform, orgasmic, outpatient,
   paroxysmal, patchy, patient, rambling, rheumatic, rough, saltatory,
   scrappy, seismic, shut-in, sick person, snatchy, spasmatic,
   spasmic, spasmodic, sporadic, spotty, staggering, sufferer,
   terminal case, the sick, twitchety, twitching, twitchy, uncertain,
   unequal, uneven, unmethodical, unmetrical, unregular, unrhythmical,
   unsettled, unsteady, unsystematic, upheaving, valetudinarian,
   variable, veering, vellicative, wandering, wavering, wobbling,
   wobbly