1derogatory The use of (or tendency to use) ad hoc measures, rather than general long-term strategies, to deal with issues, situations, etc.
Frequently in form adhocism. In the terminology of Charles Jencks (b. 1939): the practice or movement of building in a style characterized by spontaneity, invention, and individuality, in order to achieve social variety in modern cities.
1950s; earliest use found in The American Economic Review. From ad hoc + -ism.