In photography, a snoot is a tube or similar object that fits over a studio light or portable flash and allows the photographer to control the direction and radius of the light beam. These may be conical, cylindrical, or rectangular in shape. Snoots can isolate a subject when using a flash. They help by stopping "light spill", or when lighting falls in a larger footprint than intended.
References
Snoot Wikipedia(Text) CC BY-SA