Collimator: a device that narrows a beam of particles or waves. To narrow can mean either to cause the directions of motion to become more aligned in a specific direction or to cause the spatial cross section of the beam to become smaller. (Wikipedia)
Cookie: a device for casting shadows or silhouettes to produce patterned illumination. (Wikipedia)
Fresnel lens: The design allows the construction of lenses of large aperture and short focal length without the mass and volume of material that would be required by a lens of conventional design. (Wikipedia)
Gobo: a physical stencil or template that is placed inside or in front of a light source, to control the shape of the emitted light. (Wikipedia). Also sometimes used to refer to the arm on a C-Stand (‘gobo arm’) or the grip head on the arm (‘gobo head’).
Scrim: a device affixed to a light fixture to reduce the intensity of the light
Shadowfall: the surface on which a shadow is thrown. It was Andy’s idea.
Voodoo Stick: A thing, like a paint stir stick but of varying width, used to block secondary shadows from a Fresnel light fixture. Andy thought of it, I named it.
WackGaffery: Applied Physics, or, Seven Impossible Things Before Breakfast.