Metaphorically, any of the members of a group who have been there the longest (regardless of actual age or gender.)(noun)
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Use "greybeard" in a sentence
"Jack Straw - Mr Brown's loyal "greybeard" - will stay as Justice Secretary."
"Then ships bearing news might reach Alexandria by the dozen -- that is, the greybeard added with a defiant glance at the daintily clad city gentleman -- if they were allowed to pass the Pharos or go through the Poseidon basin into the Eunostus."
"The hero of the tale squeezes whey out of a piece of cheese or curd which he passes off as a stone; he induces the fleet demon to compete with his "Hop o 'my Thumb" the hare; he sets the strong demon to wrestle with his "greybeard" the bear; he frightens the"