http://en.wikipedia.org/wiki/Ad_hoc
Ad hoc is a Latin phrase meaning "for this". It generally signifies a solution designed for a specific problem or task, non-generalizable, and not intended to be able to be adapted to other purposes. Compare A priori. Common examples are organizations, committees, and commissions created at the national or international level for a specific task. In other fields the term may refer, for example, to a military unit created under special circumstances, a tailor-made suit, a handcrafted network protocol, or a purpose-specific equation. Ad hoc can also mean makeshift solutions, shifting contexts to create new meanings, inadequate planning, or improvised events.
专门的，非通用的，定制的
权宜之计，临时的，
ad-hoc testing随机测试