[1] : The Collaborative International Dictionary of English v.0.48

hark \hark\ haumrk, v. i. oe. herken. see hearken.
   to listen; to hearken. now rare, except in the imperative
   form used as an interjection, hark listen. --hudibras.
   1913 webster

   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.
      1913 webster

            he must have overshot the mark, and must hark back.
                                                  --haggard.
      1913 webster

            he harked back to the subject.        --w. e.
                                                  norris.
      1913 webster
see also:
hearken hark away hark back hark forward to hark back 

[2] : WordNet (r) 2.0

hark
     v : listen; used mostly in the imperative syn: harken, hearken
see also:
harken hearken 

[3] : Moby Thesaurus II by Grady Ward, 1.0

33 moby thesaurus words for "hark":
   nb, attend, attend to, auscultate, be all ears, bend an ear, bug,
   cock the ears, eavesdrop, examine by ear, give attention,
   give audience to, give ear, give ear to, hear, hear out, hearken,
   hearken to, heed, intercept, lend an ear, listen, listen at,
   listen in, listen to, mark, mind, note, notice, remark, sit in on,
   tap, wiretap

Hark >> H Words
Hark, definition of term: Hark
hark_pag1.html

Hark Back >> H Words
Hark Back, definition of term: Hark Back
hark+back_pag1.html