The expression is used when referring to organizations, committees, and commissions created at the national or international level for a specific task.
In judicial practice, the term defines the appointment of a judge for resolving a special case. Ad hoc can also have connotations of a makeshift solution, inadequate planning or improvised event. The solution is temporary and available for a definite period of time.
In other fields the term may refer, for example, to a military unit created under special circumstances, tailor-made suit, a communication protocol or mathematic equation with a specific purpose, which satisfies certain conditions.