obsidional
/əbˈsɪdɪənl/Now chiefly historical
adjective
1Of or relating to a siege; specifically designating a wreath of grass or weeds conferred as a mark of honour upon a Roman general who raised a siege, especially in obsidional crown, or designating coins struck, or another object serving the purpose of a coin, in a besieged town as a substitute for regular coins.
2Of disease: that assails or surrounds.
Origin
Late Middle English; earliest use found in John Lydgate (c1370–c1449), poet and prior of Hatfield Regis. From classical Latin obsidiōnālis of or relating to a siege (1st cent. a.d.) from obsidiōn-, obsidiō + -ālis.