Source : Webster's Revised Unabridged Dictionary (1913)

Undertow \Un"der*tow`\, n. (Naut.)
   The current that sets seaward near the bottom when waves are
   breaking upon the shore.

Source : WordNet®

undertow
     n 1: an inclination contrary to the strongest or prevailing
          feeling; "his account had a poignant undertow of regret"
     2: the seaward undercurrent created after waves have broken on
        the shore [syn: {sea puss}, {sea-puss}, {sea purse}, {sea-purse},
         {sea-poose}]