Compost International
Saving the earth one compost heap at a time  has an excellent glossary to supplement the one below:

Actinomycetes Microorganisms between bacteria and fungi.  They produce characteristic branched mycelium and are responsible for the earthy smell of compost.
Activator an addition to the compost pile containing nitrogen  or a source of sugars. Its purpose is to increase microbial activity by providing food.
Aerobic occuring in the presence of oxygen
Aggregates The structures or clumps formed when soil minerals and organic matter are bound together wuth the help of organic molecules, plant roots, fungi and clays
Anaerobes bacteria which do not need oxygen
Auxin a substance found in places such as plant sprouts (especially willows) and human urine which stimulates growth in plant tissues promoting root formation.  The basis of rooting powders.
Available nutrient the form of a nutrient that the plant is able to use, eg ammonium or nitrate as opposed to free nitrogen or nitrogen in an organic compound
Bacteria Single-celled microorganisms that break down organic materials in the early stages of composting. . The three types of bacteria are psychrophilic, mesophyllic, and thermophilic. It is the latter two that generate the heat associated with hot composting
Browns Carbon rich materials which provide bulk in the compost pile
Buffering The slowdown or inhibition of changes in availability of nutrients due to varying pH.  A buffer tends to neutralize both acids and alkalis through the exchange of Hydrogen ions.
C:N ratio The relative amount of total carbon to total nitrogen in a compostable material
CAC Cation Exchange Capacity:The amount of negative charge on humus and clay particles that allows them to hold on to positively charged ions (cations)
Clay Soil with extememly fine particles, less than 0.002mm
Compost organic material that has been well decomposed by organisms under conditions of good aeration.
Fertility the condition of the soil which best promotes growth
Fertilizer unless qualified with "natural" or "organic", this refers to some combination of nitrogen, phosphorus and potassium added to the soil to promote growth.
Friable crumbly, falls apart when lifted
Greens Nitrogen -rich organic matter.Any matter coming from an animal source, most specifically manures, Also green plant material, including leaves and small branches cut while green.  Dried grass clippings are still green.
Humus The very well decomposed part of the soil organic matter, made up of long chains of carbon compounds, including humic and fulvic acids. Has a high CAC
Leach To remove soluble minerals from the soil by the action of a percolating liquid, particularly rainwater                                
Loam A mixture of soil types, usually with organic material incorporated
Macro-organisms Visible creatures which live in or on the soil:worms, spiders, mites, daddy longlegs, centipedes, millipedes, all the insects, sow bugs and pill bugs, slugs and snails
Micro-organisms bacteria, fungi, protozoa, actinomycetes and nematodes.  Too small to see with the naked eye
Porosity the openess of the soil and the amount of air which can percolate through it.
Sand The coarsest form of soil with particles, visible to the human eye
Silt Soil with fine particles, 0.06mm or less
Tilth The physical condition or structure of the soil as it influences plant growth.  A soil with good tilth is very porous and allows rainfall to infiltrate easily, permits roots to grow without obstruction, and is easy to work.  In other words, how easily the soil can be tilled or otherwise worked