noun The act of reading data back from a location where it has been stored.
noun The repetition of a message one has received, in order to acknowledge it and to demonstrate accurate comprehension (especially of commands).
noun The reading aloud by a transcriptionist, court reporter, or stenographer of draft correspondence or of testimony previously taken down in dictation, usually at the request of the presiding judge or parties involved in a deposition (courtroom contexts) or of the manager dictating the correspondence (business contexts).
OK, now let's do a readback before you send this off.