[Keeper of Dol Guldur]

While that might be how every reader to read the Return of the King and how even Eowyn herself interpreted Glorfindel's words, I can't help but believe it is utterly and completely incorrect. It's obvious that the Witch-King did not recognize what the words meant either. "Not by the hand of man will he fall", said Glorfindel. Tolkien referred to Men in general as the race of Men, and Eowyn was included in that race. While she was a woman, and that does seem to be how she was able to fulfill this prophecy, I don't think it's correct. And even with Merry being a Hobbit, and closely related to the race of Men, it is still possible. "Not by the HAND OF MAN will he fall," but maybe by the HANDS OF MEN. Glorfindel's words may have meant that it had to be a group effort that brought down the Morgul Lord, because in solo combat, he was undefeatable. Obviously as an ambiguous prophecy, this is just one of many contributing factors, concerning definition of the word 'man' in his prophecy.