The Collaborative International Dictionary of English v.0.48:

Penetrate \Pen"e*trate\, v. t. [imp. & p. p. Penetrated; p.
   pr. & vb. n. Penetrating.] [L. penetratus, p. p. of
   penetrare to penetrate; akin to penitus inward, inwardly, and
   perh. to pens with, in the power of, penus store of food,
   innermost part of a temple.]
   1. To enter into; to make way into the interior of; to effect
      an entrance into; to pierce; as, light penetrates
      darkness.
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   2. To affect profoundly through the senses or feelings; to
      touch with feeling; to make sensible; to move deeply; as,
      to penetrate one's heart with pity. --Shak.
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            The translator of Homer should penetrate himself
            with a sense of the plainness and directness of
            Homer's style.                        --M. Arnold.
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   3. To pierce into by the mind; to arrive at the inner
      contents or meaning of, as of a mysterious or difficult
      subject; to comprehend; to understand.
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            Things which here were too subtile for us to
            penetrate.                            --Ray.
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