A rotating horizontal blade or sweeper mechanism installed in a coolship or shallow cooling vessel. As the hot wort sits in the wide, shallow pan to cool, the flighter slowly revolves to keep the liquid moving. This gentle agitation prevents a skin from forming on the surface, accelerates evaporation, and helps gather the coagulated trub into the center of the vessel for easier removal.
Heard on the job
Make sure the flighter is engaged while the coolship fills, otherwise the wort will stratify and take twice as long to cool.