greybeard definitions WordNet (r) 3.0 (2005) n 1: a man who is very old [syn: old man, greybeard, graybeard, Methuselah] 2: a stoneware drinking jug with a long ... of Cardinal Bellarmine (17th century) [syn: bellarmine, longbeard, long-beard, greybeard] Oxford Reference Dictionary n. archaic 1 an old man. 2 ...