the measure is ad hoc
这句话是什么意思呢？有合适的中文翻译吗，如可以附该翻译来源更好

ad hoc指的是什么，词典中说 "for this"，“it generally signifies a solution designed for a specific problem or task, non-generalizable, and not intended to be able to be adapted to other purposes (compare with a priori).”