Search Result for "siege perilous":
Wordnet 3.0

NOUN (1)

1. the legendary seat at King Arthur's Round Table reserved for the knight who would find the Holy Grail; it was fatal for anyone else to sit in it; 



WordNet (r) 3.0 (2006):

Siege Perilous
    n 1: the legendary seat at King Arthur's Round Table reserved
         for the knight who would find the Holy Grail; it was fatal
         for anyone else to sit in it