undertow

n [sing] current below the surface of the sea, moving in the opposite direction to the surface current, esp the current caused by the backward flow of a wave breaking on a beach （海面下与海面水流呈反向流动的）回流（尤指浪拍岸退回形成的）: caught in an undertow 碰上回流 * The pull of the undertow can drag swimmers out to sea. 近岸回流的冲力能把游泳的人涌到海里.

undershorts, underside, undersigned, undersized, underslung, undersold, understaffed, understand, understandable, understandably, understanding, understate, understated, understatement, understood, understudy, undertake, undertaker, undertaking, undertone, underutilize, undervalue, underwater, underwear, underweight, underwent, underworld, underwrite, underwriter, undeserved, undeservedly, undeserving, undesignated, undesirable, undesirably, undetectable, undeterred, undeveloped, undid, undies,