Dictionary
ir•re•fran•gi•ble
Pronunciation: (ir"i-fran'ju-bul), [key]—
adj.
1. not to be broken or violated; inviolable:
an irrefrangible rule of etiquette.
2. incapable of being refracted.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.