The Collaborative International Dictionary of English v.0.48:

Inquietude \In*qui"e*tude\, n. [L. inquietudo: cf. F.
   inquietude.]
   Disturbed state; uneasiness either of body or mind;
   restlessness; disquietude. --Sir H. Wotton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

inquietude
    n 1: feelings of anxiety that make you tense and irritable [syn:
         edginess, uneasiness, inquietude, disquietude]

Moby Thesaurus II by Grady Ward, 1.0:

168 Moby Thesaurus words for "inquietude":
   agitation, ailment, all-overs, angst, anguish, anxiety,
   anxiety hysteria, anxiety neurosis, anxious bench, anxious concern,
   anxious seat, anxiousness, apprehension, apprehensiveness, bluster,
   bobbery, boil, boiling, boredom, brouhaha, bustle,
   cankerworm of care, care, cheerlessness, chills of fear, churn,
   cold creeps, cold shivers, cold sweat, commotion, concern,
   concernment, conturbation, creeps, didder, discomfort,
   discomposure, discontent, dislike, disorder, displeasure, disquiet,
   disquietude, dissatisfaction, distress, disturbance, dithers,
   dread, dullness, ebullition, embroilment, emptiness, ennui,
   excitement, existential woe, fear, fear and trembling, ferment,
   fermentation, fever, feverishness, fidgetiness, fidgets, flap,
   flatness, flurry, fluster, flutter, flutteration, foment,
   foreboding, forebodingness, fume, fuss, goose bumps, gooseflesh,
   grimness, heartquake, heaving, horripilation, hubbub, hurly-burly,
   jimjams, jitters, joylessness, jumpiness, lack of pleasure,
   maelstrom, malaise, misgiving, moil, nausea, nerviness, nervosity,
   nervous strain, nervous tension, nervousness, nongratification,
   nonsatisfaction, overanxiety, painfulness, palpitation, panting,
   perturbation, pins and needles, pitapat, pitter-patter, pucker,
   quaking, quaver, quavering, quiver, quiver of terror, quivering,
   restiveness, restlessness, roil, rout, row, savorlessness, seethe,
   seething, shakes, shaking, shiver, shivers, shudder, solicitude,
   spleen, staleness, stew, stir, strain, suspense, sweat, swirl,
   tastelessness, tediousness, tedium, tension, thrill of fear, throb,
   throbbing, to-do, tremble, trembling, tremor, trepidation,
   trepidity, trouble, tumult, tumultuation, turbidity, turbulence,
   turmoil, twitter, uncomfortableness, unease, uneasiness,
   unhappiness, unpleasure, unquietness, unrest, unsatisfaction,
   upset, vexation, vexation of spirit, zeal