Some terms that I think might be good to include, to illustrate what I'm thinking:
The glossary would contain a sentence or two for each term to indicate what it is, not detailed instructions on how to do it.
Does anybody else think this would be helpful?
Blend--layering different shades of a color/colors to create a natural looking gradation between shadow and highlight.
Blackline--taking a dark color such as pure black, blackened brown, brown liner, grey liner, or any other liner and using it to outline different sections on a mini. By doing this you create more depth and an artificial break between two surfaces. This helps your eye read the mini properly.
Drybrush--Taking a dry or almost dry brush, dipping in paint, running the bristles across a papertowel leaving a little pigment on the brush. Take the brush and rub the pigment on rough surfaces on the mini. This is the quick and dirty way of adding highlights.
Glaze--A wash that is thinned out a little more. You use a glaze by painting it on rather than slathering (like you do with a wash) to help blend areas with harsh highlights.
Ink--a type of pigmented liquid used for washes and adding shadows to recessed areas. This is the quick and dirty way to get shadows.
NMM--Non-metal metallics. Using non-metallic paints to create the illusion of metallic reflectiveness.
OSL--source lighting, used to create glowing effects on a mini.
Wash--diluting regular flat paints to a consistency that will allow the pigment to run into cracks and crevices of minis.
Others that were requested . . .
SENMM-Sky Earth Non Metallic Metals, painting non-metallic metals but including a horizon line showing different types of reflections achieved if the metal was really "outside".
Demi-Metallics--using metallic paint mixed with flat paints, inks, liners, etc to tint the metallics darker or lighter. Use the same techniques as if painting non-metallics but demis will retain some of their shininess.
Complementary colors--primary colors are red, blue, yellow. secondary colors are purple, orange and green. Red + Green, Blue + Orange, Yellow + Purple = complementary colors.