Source : Webster's Revised Unabridged Dictionary (1913)

Objector \Ob*ject"or\, n. [L., an accuser.]
   One who objects; one who offers objections to a proposition
   or measure.

Source : WordNet®

objector
     n : a person who dissents from some established policy [syn: {dissenter},
          {dissident}, {protester}, {contestant}]