The Collaborative International Dictionary of English v.0.48:

Pervious \Per"vi*ous\, a. [L. pervis; per + via a way. See
   Per-, and Voyage.]
   1. Admitting passage; capable of being penetrated by another
      body or substance; permeable; as, a pervious soil.
      [1913 Webster]

            [Doors] . . . pervious to winds, and open every way.
                                                  --Pope.
      [1913 Webster]

   2. Capable of being penetrated, or seen through, by physical
      or mental vision. [R.]
      [1913 Webster]

            God, whose secrets are pervious to no eye. --Jer.
                                                  Taylor.
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   3. Capable of penetrating or pervading. [Obs.] --Prior.
      [1913 Webster]

   4. (Zool.) Open; -- used synonymously with perforate, as
      applied to the nostrils or birds.
      [1913 Webster]

WordNet (r) 3.0 (2006):

pervious
    adj 1: admitting of passage or entrance; "pervious soil"; "a
           metal pervious to heat" [ant: imperviable,
           impervious]

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "pervious":
   accessible, amenable, approachable, attainable, available,
   come-at-able, excretory, exudative, findable, getatable, gettable,
   impressionable, influenceable, leaky, malleable, movable,
   obtainable, oozy, open, open to, open-minded, openable, penetrable,
   percolative, permeable, persuadable, persuasible, plastic, pliable,
   pliant, porose, porous, procurable, reachable, receptive,
   responsive, runny, securable, suasible, suggestible, susceptible,
   swayable, to be had, transudative, weak, weepy, within reach