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]