auditor

noun

1. One who audits bookkeeping accounts.
2. In many jurisdictions, an elected or appointed public official in charge of the public accounts; a comptroller.
3. One who audits an academic course; who attends the lectures but does not earn academic credit.
4. (rare)One who listens, typically as a member of an audience.

   “There is another of better notice, and whispered through the world with some attention; credulous and vulgar auditors readily believing it, and more judicious and distinctive heads not altogether rejecting it.”

   “Thus (as you will see with half an eye, my wise little auditors) these good old dames had fallen into a strange perplexity.”

   “Sampson's tongue was still flying with rapidity, as if his auditors had not been void of a number, while Mr. Alboni and Natalie were holding a consultation aside.”

   “As we crossed the hall the telephone-bell rang, and we were the involuntary auditors of Professor Challenger's end of the ensuing dialogue.”

5. One trained to perform spiritual guidance procedures.