The Collaborative International Dictionary of English v.0.48:

Apprehend \Ap`pre*hend"\ ([a^]p`pr[-e]*h[e^]nd"), v. t. [imp. &
   p. p. Apprehended; p. pr. & vb. n. Apprehending.] [L.
   apprehendere; ad + prehendere to lay hold of, seize; prae
   before + -hendere (used only in comp.); akin to Gr.
   chanda`nein to hold, contain, and E. get: cf. F.
   appr['e]hender. See Prehensile, Get.]
   1. To take or seize; to take hold of. [Archaic]
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            We have two hands to apprehend it.    --Jer. Taylor.
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   2. Hence: To take or seize (a person) by legal process; to
      arrest; as, to apprehend a criminal.
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   3. To take hold of with the understanding, that is, to
      conceive in the mind; to become cognizant of; to
      understand; to recognize; to consider.
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            This suspicion of Earl Reimund, though at first but
            a buzz, soon got a sting in the king's head, and he
            violently apprehended it.             --Fuller.
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            The eternal laws, such as the heroic age apprehended
            them.                                 --Gladstone.
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   4. To know or learn with certainty. [Obs.]
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            G. You are too much distrustful of my truth.
            E. Then you must give me leave to apprehend
            The means and manner how.             --Beau. & Fl.
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   5. To anticipate; esp., to anticipate with anxiety, dread, or
      fear; to fear.
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            The opposition had more reason than the king to
            apprehend violence.                   --Macaulay.
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   Syn: To catch; seize; arrest; detain; capture; conceive;
        understand; imagine; believe; fear; dread.

   Usage: To Apprehend, Comprehend. These words come into
          comparison as describing acts of the mind. Apprehend
          denotes the laying hold of a thing mentally, so as to
          understand it clearly, at least in part. Comprehend
          denotes the embracing or understanding it in all its
          compass and extent. We may apprehended many truths
          which we do not comprehend. The very idea of God
          supposes that he may be apprehended, though not
          comprehended, by rational beings. "We may apprehended
          much of Shakespeare's aim and intention in the
          character of Hamlet or King Lear; but few will claim
          that they have comprehended all that is embraced in
          these characters." --Trench.
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The Collaborative International Dictionary of English v.0.48:

Apprehend \Ap`pre*hend"\, v. i.
   1. To think, believe, or be of opinion; to understand; to
      suppose.
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   2. To be apprehensive; to fear.
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            It is worse to apprehend than to suffer. --Rowe.
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WordNet (r) 3.0 (2006):

apprehend
    v 1: get the meaning of something; "Do you comprehend the
         meaning of this letter?" [syn: grok, get the picture,
         comprehend, savvy, dig, grasp, compass,
         apprehend]
    2: take into custody; "the police nabbed the suspected
       criminals" [syn: collar, nail, apprehend, arrest,
       pick up, nab, cop]
    3: anticipate with dread or anxiety [syn: apprehend, quail
       at]

Moby Thesaurus II by Grady Ward, 1.0:

111 Moby Thesaurus words for "apprehend":
   absorb, accept, anticipate, appreciate, arrest, assimilate,
   be acquainted with, be afraid, be apprised of, be aware of,
   be cognizant of, be conscious of, be conversant with, be informed,
   be sensible of, be with one, bode, bust, capture, catch, catch on,
   cognize, collar, compass, comprehend, conceive, conceptualize,
   cotton to, croak, detain, dig, digest, discern, divine, dread,
   experience, eye askance, fathom, fear, feel, follow, forebode,
   foreknow, forewarn, get, get hold of, get the drift, get the idea,
   get the picture, grab, grasp, have, have a premonition,
   have a presentiment, have information about, have it taped,
   have knowledge of, have qualms, hear, ken, know, learn, look black,
   lower, make an arrest, make out, master, menace, misgive, nab, net,
   penetrate, perceive, pick up, pinch, portend, possess,
   preapprehend, prehend, prevision, pull in, put under arrest, read,
   realize, recognize, respond, respond to stimuli, run in, savvy,
   see, seize, seize the meaning, sense, sit upon thorns, smell,
   stand aghast, take, take captive, take in, take into custody,
   take prisoner, taste, threaten, touch, tumble to, twig, understand,
   visualize, warn, wot, wot of