Auditing is one of the technical and practical subject so defining each term can be different from one perspective to other. For example, term defined in one definition might have completely different meanings in another standard. Also there are many different auditing boards around the world ranging from global to country wide organizations responsible for auditing matters in a particular economy.
I would suggest that you should consult the relevant standards that are applicable for your country or the ones that are relevant to your studies and job. Most of the time terms are defined at the start of the standard. And remember some terms may have global acceptance regarding meanings but majority of the terms have different scope and meaning under different standards issued by different auditing and accounting boards.
As many countries are using auditing standards issued by International Auditing and Assurance Standards Board (IAASB) therefore, the glossary of standards issued by IAASB might be relevant to you as well. You can download the glossary of terms as defined for IAASB standards at this link.
Again it is emphasized that you should be using the glossary of those standards which are relevant and applicable in your circumstances.