500
What are the two words in English that are said to possess the most definitions? (Tip: According to the Oxford English Dictionary: Rounding out the top ten are "go" with 368, "take" with 343, "stand" with 334, "get" with 289, "turn" with 288, "put" with 268, "fall" with 264, and "strike" with 250)
For a long time, "set" had the most meanings in the OED, but now it is "run". From the New York Times of 25th May 2011:
In the first edition of the O.E.D., in 1928, that richest-of-all-words was “set” (75 columns of type, some 200 senses), the victor in today’s rather more frantic and uncongenial world is, without a doubt, the three-letter word “run.”
... Mr. Gilliver has finally calculated that there are for the verb-form alone of “run” no fewer than 645 meanings. But more significantly still, “run” is also far bigger than the old chestnut “set,” a word that, says Mr. Gilliver, simply “hasn’t undergone as much development in the 20th and 21st centuries as has ‘run.’ ”