The Collaborative International Dictionary of English v.0.48:

Timeserving \Time"serv`ing\, a.
   Obsequiously complying with the spirit of the times, or the
   humors of those in power.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Timeserving \Time"serv`ing\, n.
   An obsequious compliance with the spirit of the times, or the
   humors of those in power, which implies a surrender of one's
   independence, and sometimes of one's integrity.
   [1913 Webster]

   Syn: Temporizing.

   Usage: Timeserving, Temporizing. Both these words are
          applied to the conduct of one who adapts himself
          servilely to times and seasons. A timeserver is rather
          active, and a temporizer, passive. One whose policy is
          timeserving comes forward to act upon principles or
          opinions which may promote his advancement; one who is
          temporizing yields to the current of public sentiment
          or prejudice, and shrinks from a course of action
          which might injure him with others. The former is
          dishonest; the latter is weak; and both are
          contemptible.
          [1913 Webster]

                Trimming and timeserving, which are but two
                words for the same thing, . . . produce
                confusion.                        --South.
          [1913 Webster]

                [I] pronounce thee . . . a hovering temporizer,
                that
                Canst with thine eyes at once see good and evil,
                Inclining to them both.           --Shak.
          [1913 Webster]

WordNet (r) 3.0 (2006):

timeserving
    adj 1: taking immediate advantage, often unethically, of any
           circumstance of possible benefit [syn: opportunist,
           opportunistic, timeserving]