To go to extremes; to overreact, especially in favor of something or someone. This expression, which conjures up the extreme act of jumping or falling off a ship, dates from the first half of the twentieth century. For a time it signified living beyond one’s means, but that meaning is no longer current. John P. Marquand used the term in its contemporary sense (Melville Goodwin, 1951): “Did you ever hear about General Goodwin going overboard over an American girl in Paris?”