HANDS DOWN (also see Ask the Wordwizard'shands down), as in WON HANDS DOWN, means very easily, without effort <“He WON the election HANDS DOWN.”>. It also can mean without question, undoubtedly. <“He is hands down the best surgeon in his field.>.
The term comes from horse racing, where a jockey would drop his hands and relax his hold on the reins when victory appeared certain. This is akin to the bicycle racing gesture when, assured of victory, the rider raises his/her hands above the head (they never did call it ‘winning hands up’!) as the finish line is approached and crossed. In my 35 years of racing, I didn’t do much of that, but I watched it a lot. (<:) Anyway, the term first appeared in print in 1867 and is still used in reference to various kinds of competition.
In the U.S. if someone said ‘he was BEATEN HANDS DOWN,’ it would usually mean ‘he was beaten easily, without effort, at least according to most dictionaries (including the OED, M-W, etc., etc.). However, some dictionaries provide other meanings and if one looks at the context in which this phrase is used, it seems to me that it is impossible to tell what the person saying it really meant. Which of the legitimate meanings were they referring to? Did they mean 'easily' or did they mean 'undoubtedly,' 'conclusively,' or 'completely?' The Cambridge Advanced Learner’s Dictionary provides the following quote under the headword BEAT:<1867 “There were good horses in those days, as he can well recall, But Barker upon Elepoo, HANDS DOWN, shot by them all.”—‘Lyrics & Lays’ by Pips, page 155>
<1882 “(caption) WON!! ‘HANDS DOWN.’”—‘Moonshine,’ 3 June, page 265>
<1913 “That I should surrender, HANDS DOWN, to a lot of trumpery complaints and grievances.”—‘The Mating of Lydia’ by Mrs. H. Ward, II. xii>
<1935 “IN the North Caucasus especially, where ‘the spirit of individualism’ is strongest, resistance to agrarian reform was the most stubborn. Nevertheless, the reform has WON HANDS DOWN—than which, short of actual war, there could be little more important news from the U. S. S. R.”—‘New York Times, 1 September, page F8>
<1958 “Double this speed, however, and the submarine WINS HANDS DOWN.”—‘Times,’ 14 August, page 9/7>
<1996 “ But in its [[liberalism’s]] competition with conservative thinking for the soul of America, it has WON HANDS DOWN.”—‘New York Times,’ 24 January, page SM33>
So, I am going to have to agree with Wiz that “beaten hands down” can mean ‘defeated conclusively,’ as well as ‘easily,’ and it seems to me that in most situations it would be very difficult to know which was meant, as illustrated in the following historical examples:<“They were beaten HANDS DOWN (= COMPLETELY) by their opponents.”>
Ken G – September 10, 2005<1911 “They [[the organizations of the French and German colonies in Mexico]] have us BEATEN HANDS DOWN in the matter of yachting caps and cavalry leggings, so dear to the improvised infantryman.”—‘New York Times,’ 14 May, page 1>
<1928 “’The Tammany Administration [[NYC Democratic political machine]] elected on the five-cent fare issue, has let itself be BEATEN HANDS DOWN all over the sidewalks of New York,’ the paper reads.”—‘New York Times,’ 7 May, page 1>
<1965 “But what if the older generations follow President Johnson’s lead and assure the young the old-timers had them BEATEN HANDS-DOWN at immorality.”—‘New York Times,’ 7 August, page 34>
<1984 “‘He [[Ronald Reagan]] was just BEATEN HANDS DOWN in that debate by Walter Mondale,’ Dixon said.”—‘Chicago Tribune,’ 19 October, page 22>