The Collaborative International Dictionary of English v.0.48:

Obverse \Ob*verse"\ ([o^]b*v[~e]rs"), a. [L. obversus, p. p. of
   obvertere. See Obvert.]
   Having the base, or end next the attachment, narrower than
   the top, as a leaf.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Obverse \Ob"verse\ ([o^]b"v[~e]rs), n. [Cf. F. obverse, obvers.
   See Obverse, a.]
   1. The face of a coin which has the principal image or
      inscription upon it; -- the other side being the
      reverse.
      [1913 Webster]

   2. Anything necessarily involved in, or answering to,
      another; the more apparent or conspicuous of two possible
      sides, or of two corresponding things.
      [1913 Webster]

            The fact that it [a belief] invariably exists being
            the obverse of the fact that there is no alternative
            belief.                               --H. Spencer.
      [1913 Webster]

WordNet (r) 3.0 (2006):

obverse
    n 1: the more conspicuous of two alternatives or cases or sides;
         "the obverse of this issue"
    2: the side of a coin or medal bearing the principal stamp or
       design [ant: reverse, verso]

Moby Thesaurus II by Grady Ward, 1.0:

150 Moby Thesaurus words for "obverse":
   adversative, adverse, adversive, ally, alter ego, analogon,
   analogue, antagonistic, anteriority, anti, antipathetic, antipodal,
   antipode, antipodes, antipole, antithesis, antithetic, antonym,
   antonymous, associate, at cross-purposes, balancing, bold front,
   brave face, brave front, brother, clashing, close copy,
   close match, cognate, companion, compensating, complement,
   conflicting, confronting, congenator, congener, contra,
   contradictory, contradistinct, contrapositive, contrarious,
   contrary, contrasted, converse, coordinate, correlate, correlative,
   correspondent, counter, counterbalance, counterbalancing,
   countercheck, counterpart, counterpoint, counterpoise,
   counterpoised, counterpole, counterterm, countervailing,
   dead against, discordant, discrepant, display, equivalent,
   eyeball to eyeball, eyeball-to-eyeball, facade, face, facet, facia,
   facing, fellow, foil, fore, forefront, foreground, forehand,
   foreland, forepart, forequarter, foreside, foreword, front,
   front elevation, front man, front matter, front page, front view,
   frontage, frontal, frontier, frontispiece, head, heading, heads,
   hostile, image, inconsistent, inimical, inverse, kindred spirit,
   lap, like, likeness, mate, near duplicate, offset, opposed,
   opposing, opposite, opposite number, opposite side, oppositional,
   oppositive, oppugnant, other face, other side, parallel, pendant,
   perverse, picture, polar, polaric, polarized, preface, prefix,
   priority, proscenium, reciprocal, repugnant, reverse, second self,
   setoff, similitude, simulacrum, sister, soul mate, squared off,
   such, suchlike, tails, tally, the contrary, the like of,
   the likes of, the other side, twin, vis-a-vis, window dressing