fossilized, fossilised, ossified - set in a rigidly conventional pattern of behavior, habits, or beliefs; "obsolete fossilized ways"; "an ossified bureaucratic system" Antonym:flexible (indirect, via inflexible)
rigidify, ossify, petrify - make rigid and set into a conventional pattern; "rigidify the training schedule"; "ossified teaching methods"; "slogans petrify our thinking" --2is one way tostiffen