The Collaborative International Dictionary of English v.0.48:

Inner \In"ner\ ([i^]n"n[~e]r), a. [AS. innera, a compar. fr.
   inne within, fr. in in. See In.]
   1. Further in; interior; internal; not outward; as, an inner
      chamber.
      [1913 Webster]

   2. Of or pertaining to the spirit or its phenomena.
      [1913 Webster]

            This attracts the soul,
            Governs the inner man, the nobler part. --Milton.
      [1913 Webster]

   3. Not obvious or easily discovered; obscure.
      [1913 Webster]

   Inner house (Scot.), the first and second divisions of the
      court of Session at Edinburgh; also, the place of their
      sittings.

   Inner jib (Naut.), a fore-and-aft sail set on a stay
      running from the fore-topmast head to the jib boom.

   Inner plate (Arch.), the wall plate which lies nearest to
      the center of the roof, in a double-plated roof.

   Inner post (Naut.), a piece brought on at the fore side of
      the main post, to support the transoms.

   Inner square (Carp.), the angle formed by the inner edges
      of a carpenter's square.
      [1913 Webster]

WordNet (r) 3.0 (2006):

inner
    adj 1: located inward; "Beethoven's manuscript looks like a
           bloody record of a tremendous inner battle"- Leonard
           Bernstein; "she thinks she has no soul, no interior life,
           but the truth is that she has no access to it"- David
           Denby; "an internal sense of rightousness"-
           A.R.Gurney,Jr. [syn: inner, interior, internal]
    2: located or occurring within or closer to a center; "an inner
       room" [ant: outer(a)]
    3: innermost or essential; "the inner logic of Cubism"; "the
       internal contradictions of the theory"; "the intimate
       structure of matter" [syn: inner, internal, intimate]
    4: confined to an exclusive group; "privy to inner knowledge";
       "inside information"; "privileged information" [syn:
       inside, inner, privileged]
    5: exclusive to a center; especially a center of influence;
       "inner regions of the organization"; "inner circles of
       government"
    6: inside or closer to the inside of the body; "the inner ear"

Moby Thesaurus II by Grady Ward, 1.0:

69 Moby Thesaurus words for "inner":
   absolute, central, certain, close, concealed, concrete,
   constitutional, deep, deep-seated, defined, definite, detailed,
   determinate, different, distinct, distinguished, esoteric,
   especial, essential, exceptional, express, extraordinary, familiar,
   fixed, focal, gut, hidden, immanent, implanted, implicit,
   inalienable, individual, indoor, indwelling, infixed, ingrained,
   inherent, inmost, innermost, inside, interior, internal, intestine,
   intimate, intrinsic, inward, inwrought, irreducible, middle,
   minute, noteworthy, nuclear, particular, personal, precise,
   private, resident, respective, secret, several, singular,
   solipsistic, special, specific, subjective, unalienable,
   unchallengeable, unquestionable, visceral