The Collaborative International Dictionary of English v.0.48:

However \How*ev"er\, adv. [Sometimes contracted into howe'er.]
   1. In whetever manner, way, or degree.
      [1913 Webster]

            However yet they me despise and spite. --Spenser.
      [1913 Webster]

            Howe'er the business goes, you have made fault.
                                                  --Shak.
      [1913 Webster]

   2. At all events; at least; in any case.
      [1913 Webster]

            Our chief end is to be freed from all, if it may be,
            however from the greatest evils.      --Tillotson.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

However \How*ev"er\, conj.
   Nevertheless; notwithstanding; yet; still; though; as, I
   shall not oppose your design; I can not, however, approve of
   it.
   [1913 Webster]

         In your excuse your love does little say;
         You might howe'er have took a better way. --Dryden.

   Syn: However, At least, Nevertheless, Yet.

   Usage: These words, as here compared, have an adversative
          sense in reference to something referred to in the
          context. However is the most general, and leads to a
          final conclusion or decision. Thus we say, the truth,
          however, has not yet fully come out; i.e., such is the
          speaker's conclusion in view of the whole case. So
          also we say, however, you may rely on my assistance to
          that amount; i. e., at all events, whatever may
          happen, this is my final decision. At least is
          adversative in another way. It points out the utmost
          concession that can possibly be required, and still
          marks the adversative conclusion; as, at least, this
          must be done; whatever may be our love of peace, we
          must at least maintain the rights of conscience.
          Nevertheless denotes that though the concession be
          fully made, it has no bearing of the question; as,
          nevertheless, we must go forward. Yet signifies that
          however extreme the supposition or fact comceded may
          be, the consequence which might naturally be expected
          does not and will not follow; as, though I should die
          with thee, yet will I not deny thee; though he slay
          me, yet will I trust in him. Cf. But.
          [1913 Webster]

WordNet (r) 3.0 (2006):

however
    adv 1: despite anything to the contrary (usually following a
           concession); "although I'm a little afraid, however I'd
           like to try it"; "while we disliked each other,
           nevertheless we agreed"; "he was a stern yet fair
           master"; "granted that it is dangerous, all the same I
           still want to go" [syn: however, nevertheless,
           withal, still, yet, all the same, even so,
           nonetheless, notwithstanding]
    2: by contrast; on the other hand; "the first part was easy; the
       second, however, took hours"
    3: to whatever degree or extent; "The results, however general,
       are important"; "they have begun, however reluctantly, to
       acknowledge the legitimacy of some of the opposition's
       concerns"
    4: in whatever way or manner; "Victory, however it was brought
       about, was sweet"; "however he did it, it was very clever"

Moby Thesaurus II by Grady Ward, 1.0:

42 Moby Thesaurus words for "however":
   after all, again, albeit, all the same, although, anyhow, anyway,
   anywise, at all, at all events, at any rate, but, by any means,
   come what may, even, even so, except, for all that, how, howbeit,
   in any case, in any event, in any way, in what way, irregardless,
   just the same, nevertheless, no matter how, no matter what, nohow,
   nonetheless, notwithstanding, on, per contra, rather, regardless,
   save, still, though, when, yet, yowl