The Collaborative International Dictionary
Hark \Hark\ (h[aum]rk), v. i. [OE. herken. See Hearken.]
To listen; to hearken. [Now rare, except in the imperative
form used as an interjection, Hark! listen.]
Hark away! Hark back! Hark forward! (Sporting), cries used to incite and guide hounds in hunting.
To hark back, to go back for a fresh start, as when one has wandered from his direct course, or made a digression.
He must have overshot the mark, and must hark back.
He harked back to the subject.
--W. E. Norris.