Ad hoc duties are tasks designed to address a particular and clearly defined situation or responsibility. For example, a government-appointed special prosecutor would be performing ad hoc duties in the investigation and prosecution of the case to which he or she is assigned.
Often job listings include a line stating that a position is responsible for ad hoc duties as assigned. This line ensures a job applicant is aware he or she will have to take on special duties that are not otherwise listed in the job requirements. Entire positions may also be on an ad hoc, or temporary, basis. "Ad hoc" comes from the Latin phrase for "as needed."