stirrer

Short definition from Wiktionary

Noun

1. 1
   A device used to stir. (Cardinal types include wood or plastic strips (for beverages) and magnetic objects that react to a spinning magnet nearby (for chemistry beakers).
2. 2
   A person who stirs something.
3. 3
   A person who spreads rumours or causes agitation.
4. 4
   One who stirs or moves about, as after sleep.