Definition of AD HOC 1a : concerned with a particular end or purpose committee> b : formed or used for specific or immediate problems or needs < ad hoc solutions> 2: fashioned from whatever is immediately available : improvised hoc parades and demonstrations — Nat Hentoff> Examples of AD HOC The mayor appointed an ad hoc committee to study the project. We had to make some ad hoc changes to the plans. We'll hire more staff on an ad hoc basis.