The Collaborative International Dictionary of English v.0.48:

Connotation \Con`no*ta"tion\ (k[o^]n`n[-o]*t[=a]"sh[u^]n), n.
   [Cf. F. connotation.]
   The act of connoting; a making known or designating something
   additional; implication of something more than is asserted.
   [1913 Webster]

   2. a meaning implied but not explicitly denoted by some word
      or expression, which may be understood in addition to the
      explicit primary meaning.
      [PJC]

   3. (Logic) the full set of necessary properties possessed by
      all the objects within the extension of a term; the
      intensional meaning of a term, which determines the
      objects to which the term applies; the intension of a
      term.

   Syn: intension. [PJC]

WordNet (r) 3.0 (2006):

connotation
    n 1: what you must know in order to determine the reference of
         an expression [syn: intension, connotation]
    2: an idea that is implied or suggested