- a vacant seat at the Round Table that could be filled only by the predestined finder of the Holy Grail and was fatal to pretenders.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- (in Arthurian legend) the seat at the Round Table that could be filled only by the knight destined to find the Holy Grail and that was fatal to anyone else
from siege (in the archaic sense: a seat or throne)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012