The Collaborative International Dictionary of English v.0.48:

Apprehensive \Ap`pre*hen"sive\, a. [Cf. F. appr['e]hensif. See
   Apprehend.]
   1. Capable of apprehending, or quick to do so; apt;
      discerning.
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            It may be pardonable to imagine that a friend, a
            kind and apprehensive . . . friend, is listening to
            our talk.                             --Hawthorne.
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   2. Knowing; conscious; cognizant. [R.]
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            A man that has spent his younger years in vanity and
            folly, and is, by the grace of God, apprehensive of
            it.                                   --Jer. Taylor.
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   3. Relating to the faculty of apprehension.
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            Judgment . . . is implied in every apprehensive act.
                                                  --Sir W.
                                                  Hamilton.
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   4. Anticipative of something unfavorable' fearful of what may
      be coming; in dread of possible harm; in expectation of
      evil.
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            Not at all apprehensive of evils as a distance.
                                                  --Tillotson.
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            Reformers . . . apprehensive for their lives.
                                                  --Gladstone.
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   5. Sensible; feeling; perceptive. [R.]
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            Thoughts, my tormentors, armed with deadly stings,
            Mangle my apprehensive, tenderest parts. --Milton.
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WordNet (r) 3.0 (2006):

apprehensive
    adj 1: quick to understand; "a kind and apprehensive friend"-
           Nathaniel Hawthorne [syn: apprehensive, discerning]
    2: mentally upset over possible misfortune or danger etc;
       "apprehensive about her job"; "not used to a city and worried
       about small things"; "felt apprehensive about the
       consequences" [syn: apprehensive, worried]
    3: in fear or dread of possible evil or harm; "apprehensive for
       one's life"; "apprehensive of danger"

Moby Thesaurus II by Grady Ward, 1.0:

74 Moby Thesaurus words for "apprehensive":
   afraid, agitated, alive, all nerves, all-knowing, all-overish,
   anxious, anxioused up, apperceptive, appercipient, apprehending,
   awake, aware, bothered, cognizant, comprehending, concerned,
   conscious, disquieted, disturbed, edgy, excitable, fearful,
   foreboding, frightened, high-strung, in a pucker, in a stew,
   in suspense, insightful, intelligent, irritable, keyed-up, knowing,
   knowledgeable, mindful, misgiving, nerves on edge, nervous, nervy,
   omniscient, on edge, on tenterhooks, on tiptoe, overanxious,
   overapprehensive, overstrung, panicky, perceptive, percipient,
   perspicacious, perturbed, prehensile, qualmish, qualmy, quivering,
   sagacious, sensible, sentient, shrewd, solicitous, strained,
   suspenseful, taut, tense, troubled, understanding, uneasy, ware,
   wise, with bated breath, with muscles tense, witting, zealous