Formed or used for a particular purpose or for immediate needs.
Example:
The faculty formed an ad hoc committee to deal with the question of first-amendment rights on campus.
Ad hoc literally means "for this" in Latin, a meaning clearly reflected in its uses in English. An ad hoc investigating committee is authorized to look into a matter of limited scope and not to go on a fishing expedition for other wrongdoing. An ad hoc ruling by an athletic council is intended to settle a particular case, and is not meant to serve as a model for later rulings. Problems that come up in the course of a project often require immediate, ad hoc solutions.