What is Ad Hoc?

Legal Definition
Ad hoc is a Latin phrase meaning "for this". In English, 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 with a priori).

Common examples are ad hoc organizations, committees, and commissions created at the national or international level for a specific task. In other fields, the term could 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[1].
-- Wikipedia
Legal Definition
"For this". 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.
Legal Definition
For this; for this special purpose. An attorney ad hoe or a guardian or curator ad hoc, is one appointed for a special purpose, generally to represent the client or infant in the particular action in which the appointment is made. Sallier v. Rosteet, 108 La. 378, 32 South. 383; Bienvenu v. Insurance Co., 33 La. Ann. 212.
-- Black's Law Dictionary