General Breeding Terms:
Compensatory mating: Choosing hybrid parents based on a weakness in one parent. For example, we often choose G13 as a parent when we have a sativa that is quite nice to smoke, but stretchy and long flowering. G13 brings down flowering time and height, without having much impact on the smell or high, except that it tends to boost potency. Another example might be choosing Grapefruit to cross to an indica that is potent, but lacks flavor or 'bag appeal'. Fem breeding makes it easier to choose parents for compensatory mating as both parents can be evaluated for the trait of interest.
Stabilizing Selection: Growing a large number of a a segregating population and selecting the average phenotypes, culling the extreme phenos, in order to lessen the variability in the line. Usually a later step after a line produces some, but not all, exceptional plants. Not used often enough in Cannabis breeding. An example of this would be growing a thousand Love Potions and culling everything that showed a single male flower, so that the genetics of the line would be essentially unchaged, but interesex plants will eventually be completely eliminated.
Directional Selection: Choosing breeding parents based on a desire to boost a trait that is present in both. For example, if you grew out 100 F2's and selected the most purple ones for future breeding, youwould be breeding in the direction of more purpleness without any regard for other phenotypes. When working with very small populations, I believe it is best to focus on one trait a time, rather than trying to find your grail in a population of 30 or 50 beans.
Diversifying Selection: this is a concept more often used in nature, where one populations splits into two and then diverges due to different selective pressures. For example, early humans mated with chimpanzees for many centuries before the different selective pressures caused the two populations to diverge and become reproductively isolated from one another. For Cannabis breeders, this technique could be used to tease out the parent lines from an F1 hybrid. If you bought Thunderfuck Haze, and you had a good eye for both parental phenos, you could eventually have a truebreeding Thunderfuck line and a Haze line that would be more like the parents than like the original F1.
Robustness: A strain that produces similar phenotypes in a wide range of enviroments is said to be robust.
Variability: A measure of the differences in phenotypes within a strain. Some variability is good, for example if you want to harvest over a period of a week or 10 days instead of all at once. Much variablity is bad, for example if your closet has to contain plants that range from 2'-5' tall, or if your harvest window is 2 months instead of 2 weeks and you have other stuff to grow.
Stability: Another way to measure differences in phenotypes. The opposite of Variability.
Diversity: A measure of the genetic diversity within a population. The trick of the breeder is to maximize diversity while minizming variability. Diversity is necessary to allow plants to resist fungi and other pathogens, and to have genetic reserves that will allow the to slowly adapt to a changing climate in the years to come.
Stable Generation: A true F1 made between inbred parents, or a cross between two individuals of the same IBL, will produce seeds that are consistent from plant to plant. F1 plants will grow alike, but will not breed true. IBL's grow alike and will produce offspring that grow alike, both to each other and to the parents. Crossing an IBL to an F1 will produce intermediate results and is a good technique if you have the capacity to evaluate the offspring, or if you are looking for more than one keeper pheno in the progeny.
Segregating Generations: A cross between two hybrids will produce a wide range of phenotypes, especially if the hybrid grandparents are widely unrelated. Segregating generations are where the breeder goes to work, sorting through hundreds of plants to find the ones that meet the goal of the program. Most seeds on the market today are segregating generations.