1. An air-moving device composed of a wheel or blade and housing or orifice plate.
2. During construction or demolition of a building, an upwardly projecting arrangement of scaffolding and netting that is intended to catch any debris that might otherwise fall to the ground. Also see axial-flow fan, centrifugal fan, plenum fan, propeller fan, return fan, supply fan, tubeaxial fan, vaneaxial fan.