The Collaborative International Dictionary of English v.0.48:

Apprehension \Ap`pre*hen"sion\, n. [L. apprehensio: cf. F.
   appr['e]hension. See Apprehend.]
   1. The act of seizing or taking hold of; seizure; as, the
      hand is an organ of apprehension. --Sir T. Browne.
      [1913 Webster]

   2. The act of seizing or taking by legal process; arrest; as,
      the felon, after his apprehension, escaped.
      [1913 Webster]

   3. The act of grasping with the intellect; the contemplation
      of things, without affirming, denying, or passing any
      judgment; intellection; perception.
      [1913 Webster]

            Simple apprehension denotes no more than the soul's
            naked intellection of an object.      --Glanvill.
      [1913 Webster]

   4. Opinion; conception; sentiment; idea.
      [1913 Webster]

   Note: In this sense, the word often denotes a belief, founded
         on sufficient evidence to give preponderation to the
         mind, but insufficient to induce certainty; as, in our
         apprehension, the facts prove the issue.
         [1913 Webster]

               To false, and to be thought false, is all one in
               respect of men, who act not according to truth,
               but apprehension.                  --South.
         [1913 Webster]

   5. The faculty by which ideas are conceived; understanding;
      as, a man of dull apprehension.
      [1913 Webster]

   6. Anticipation, mostly of things unfavorable; distrust or
      fear at the prospect of future evil.
      [1913 Webster]

            After the death of his nephew Caligula, Claudius was
            in no small apprehension for his own life.
                                                  --Addison.
      [1913 Webster]

   Syn: Apprehension, Alarm.

   Usage: Apprehension springs from a sense of danger when
          somewhat remote, but approaching; alarm arises from
          danger when announced as near at hand. Apprehension is
          calmer and more permanent; alarm is more agitating and
          transient.
          [1913 Webster]

WordNet (r) 3.0 (2006):

apprehension
    n 1: fearful expectation or anticipation; "the student looked
         around the examination room with apprehension" [syn:
         apprehension, apprehensiveness, dread]
    2: the cognitive condition of someone who understands; "he has
       virtually no understanding of social cause and effect" [syn:
       understanding, apprehension, discernment, savvy]
    3: painful expectation [syn: apprehension, misgiving]
    4: the act of apprehending (especially apprehending a criminal);
       "the policeman on the beat got credit for the collar" [syn:
       apprehension, arrest, catch, collar, pinch, taking
       into custody]

Moby Thesaurus II by Grady Ward, 1.0:

186 Moby Thesaurus words for "apprehension":
   IQ, Pyrrhonism, abduction, agitation, alarm, all-overs, angst,
   anxiety, anxiety hysteria, anxiety neurosis, anxious bench,
   anxious concern, anxious seat, anxiousness, apprehensiveness,
   arrest, arrestation, arrestment, boding, bust, caliber,
   cankerworm of care, capacity, capture, care, catch, catching,
   clairvoyance, cliff-hanging, collaring, command, comprehension,
   conceit, concept, conception, conceptualization, concern,
   concernment, coup, deductive power, detention, diffidence,
   disquiet, disquietude, distress, distrust, distrustfulness,
   disturbance, doubt, doubtfulness, dragnet, dread, dubiety,
   dubiousness, esemplastic power, expectant waiting, faith, fancy,
   fear, forcible seizure, foreboding, forebodingness, foreknowledge,
   grab, grabbing, grasp, grip, half-belief, hold, idea, ideation,
   image, imago, impression, inquietude, integrative power, intellect,
   intellection, intellectual grasp, intellectual object,
   intellectual power, intellectualism, intellectuality, intelligence,
   intelligence quotient, kidnapping, knowledge, leeriness, malaise,
   mastery, memory-trace, mental age, mental capacity, mental grasp,
   mental image, mental impression, mental ratio, mentality, misdoubt,
   misgiving, mistrust, mistrustfulness, mother wit, nab, nabbing,
   native wit, nervous strain, nervous tension, nervousness, netting,
   notion, observation, opinion, overanxiety, panic, perception,
   perturbation, pessimism, picking up, pickup, pinch,
   pins and needles, possession, power grab, power of mind,
   precognition, prehension, premonition, prenotion, presage,
   presentiment, pucker, qualm, qualmishness, question, rationality,
   reasoning power, recept, reflection, reliance, representation,
   running in, sanity, savvy, scope of mind, scruple, scrupulousness,
   seizure, seizure of power, self-doubt, sense, sentiment,
   shadow of doubt, skepticalness, skepticism, snatch, snatching,
   solicitude, stew, strain, supposition, suspense, suspicion,
   suspiciousness, taking in, taking into custody, tension, theory,
   thinking power, thought, total skepticism, trouble, trust,
   uncertainty, understanding, unease, uneasiness, unquietness, upset,
   vexation, waiting, wariness, wisdom, wit, worry, zeal



Bouvier's Law Dictionary, Revised 6th Ed (1856):

APPREHENSION, practice. The capture or arrest of a person. The term
apprehension is applied to criminal cases, and arrest to civil cases; as,
one having authority may arrest on civil process, and apprehend on a
criminal warrant.